Objectives: Adequacy and quality of sleep have great importance in the mental functions of young adults. It is accepted that 7-8 hours is sufficient for normal physiological sleep. Sleep disorders lead to various cognitive problems and weakening in academic performance. In our study, the effects of differences in sleep duration on cognitive functions, especially on working memory and verbal skills, were investigated in medical school students. Materials and Methods: Participants were selected on a voluntary basis (n=50; 27 females, 23 males) among right-handed medical school students (with a hand preference score between 13 and 17). After the online questionnaire was applied, the participants were divided into three groups according to their sleep duration: 1. Low sleepers (LS) (≤6 hours) (n=10) 2. Normal sleepers (NS) (7-8 hours) (n=28) 3. Excessive sleepers (ES) (≥9 hours) (n=12). The Modified Corsi Block Tapping (CBT) test and Verbal Fluency test (VFT) were administered to the participants. Results: It was observed that CBT data in both the right and left handed participants were significantly decreased in the LS group compared to the NS group. There was no significant difference between the NS and ES groups. No significant difference was found between the groups in all parameters in the VFT data. Conclusion: Decreased sleep duration decreased working memory performance in line with the literature. Our results underline the impairments that may occur in working memory in individuals who cannot sleep for a sufficient amount of time. It indicates that verbal fluency is not affected by sleep duration in young medical faculty students. It would be beneficial to examine the study by expanding it with tests that can measure the effect of sleep on working memory, learning processes and other similar cognitive functions in groups with characteristics such as different ages and education levels.