Objective. Coffee drinking is the main source of caffeine intake among adult population in the western world. It has been reported that low to moderate caffeine intake has beneficial effect on alertness and cognitive functions in healthy subjects. The aim of this study is to evaluate the impact of habitual coffee consumption on cognitive function in hemodialysis patients. Methods. In a cross-sectional study, 86 patients from a single-dialysis centre underwent assessment by the Montreal Cognitive Assessment tool and evaluation for symptoms of fatigue, mood, and sleep disorders by well-validated questionnaires. The habitual coffee use and the average daily caffeine intake were estimated by participants' response to a dietary questionnaire. Results. Sixty-seven subjects (78%) consumed black coffee daily, mostly in low to moderate dose. Cognitive impairment was found in three-quarters of tested patients. Normal mental performance was more often in habitual coffee users (25% versus 16%). Regular coffee drinkers achieved higher mean scores on all tested cognitive domains, but a significant positive correlation was found only for items that measure attention and concentration (P = 0.024). Conclusions. Moderate caffeine intake by habitual coffee consumption could have beneficial impact on cognitive function in hemodialysis patients due to selective enhancement of attention and vigilance. The aim of this study is to evaluate the impact of habitual coffee consumption on cognitive function in hemodialysis patients. Methods. In a cross-sectional study, 86 patients from a single-dialysis centre underwent assessment by the Montreal Cognitive Assessment tool and evaluation for symptoms of fatigue, mood, and sleep disorders by well-validated questionnaires. The habitual coffee use and the average daily caffeine intake were estimated by participants' response to a dietary questionnaire. Results. Sixty-seven subjects (78%) consumed black coffee daily, mostly in low to moderate dose. Cognitive impairment was found in three-quarters of tested patients. Caffeine (1,3,7-trimethylxanthine) is the most important and most extensively studied compound in coffee. The presumed stimulant effect of caffeine on physiological and mental states accounts for the habit-forming nature of coffee and is the main reason for the growing popularity of caffeinated beverages. The amount of caffeine available in prepared beverage is variable and principally depends on a proportion of the mix between two primary types of coffee beans, the preparation method, and the size of the coffee cup. It is estimated that ingestion of a single cup of coffee provides doses from 0.4 to 2.5 mg of caffeine per kilogram. Since none of the responders reported the regular intake of other caffeinated beverages or food besides black coffee, we equated its using with the total amount of caffeine. Those study subjects drinking at least one cup of coffee per day were further asked to classify their usual method of preparing coffee and the size of serving cup. We assessed the total intake of caffeine by summing the caffeine content for a specific amount, depending on the preparation method and cup size, multiplied by the frequency of its use. The estimated caffeine content per single cup was 120 mg, based on data about type and an average serving size of brewed black coffee consumed in Serbia. 2.6. P values less than .05 were considered statistically significant. 3. Results More than three-quarters (78%) of the eighty-six eligible study participants consumed black coffee on a regular basis. In the group of sixty-seven regular coffee drinkers, low use (1 cup/day) was reported by 36% ( n = 24), moderate use (2 cups/day) by 40% ( n = 27), and intake of more than 2 cups a day by 24% ( n = 16) of the examined patients. Only two patients (3%) have reported heavy coffee use (≥5 cups/day) on a regular basis. The estimated adjusted amount of consumed caffeine, which almost exclusively came through ingestion of separate portions of black coffee, was 3.4 mg/kg/day (250 mg). There was no statistical significant difference in the habitual coffee drinking and total amount of ingested caffeine comparing fifteen patients who met exclusion criteria and the patients included in the study. More than 90% of habitual users in our study reported drinking coffee predominantly in the morning and early afternoon, which is followed by overnight abstinence. There were no significant differences in demographics, clinical characteristics, lifestyle factors, and selected medical comorbidities between persons who drink coffee daily and noncoffee users. Prevalence of subjects with less than 8 years of education did not differ substantially between noncoffee and regular coffee drinkers. Group comparisons are shown in This is clinically relevant because the patients with ESRD had significant deficit on measures of attention [ 30 ]. Attention and concentration help us to select and focus on what is important by modifying neural activity in specific cortical areas, thus augmenting the cerebral response to particular perceptual stimuli [ 31 ]. Caffeine influences stimulus processing and enhances vigilance by increasing cortical activation and the rate at which information accumulates. Thus, the regular caffeine intake by coffee drinking may effectively modulate the encoding and long term retrieval of memories by enhancing sustained attention [ 32 , 33 ]. The strengths of this study include the well-defined single center subject sample, a comprehensive estimation of cognitive function, and standardized evaluations of mood state, sleep disturbance, and level of fatigue. In addition, all MoCA evaluations were administered by a single physician. Finally, it should be noted that, even though in public perception and our paper the terms coffee and caffeine are interchangeable, the biologic effects of coffee cannot be reduced to the isolated effects of caffeine that it contains [ 38 ]. 5.