The aim of the study was to investigate the psychological features, sleep quality and daytime sleepiness of different chronotypes in healthy young participants. Seventy-nine female and 63 male medical students aged between 17 and 23 years (mean age: 19.8 ± 1.3 years) participated voluntarily in this study. They completed the Morningness-Eveningness Questionnaire, self-reported symptom inventory SCL-90-R, the Pittsburgh Sleep Quality Index and the Epworth Sleepiness Scale. Psychological symptoms and sleep features of morning types, evening types and intermediate types were compared with each other. Out of 141 subjects, 30 were evening types (21%), 34 were morning types (24%) and 77 were intermediate types (55%). Positive-symptom total scores of SCL-90-R were higher in the evening types than the morning and intermediate types. There were significant differences in the psychological symptoms of anxiety, obsessive-compulsiveness, hostility and phobia among these groups (p < 0.05). Total sleep quality was poorer and daytime sleepiness was significantly higher in the evening types than the morning and intermediate types (p < 0.05). Our findings suggest that evening chronotypes suffer from more anxiety, obsessive-compulsiveness, hostility and phobia symptoms, sleep problems and daytime sleepiness than the other chronotypes. © 2008 Taylor & Francis.