Abstract Background and purpose: The aim of this paper is to conduct a survey based on a questionnaire that would characterize nighttime and daytime habits in medical students; to estimate how subjective sleep quality is associated with nighttime and daytime habits and sleep problems in students; to estimate how academic progress and workload is associated with subjective sleep quality, nighttime and daytime habits and sleep problems in students; and to estimate the prevalence of self-reported sleep problems in Estonian medical students. Patients and methods: The study group included 413 medical students of the University of Tartu, aged 19-33 years. The self-reported Sleep and Daytime Habits Questionnaire (S&DHQ) covered demographic characteristics (4 questions) and sleep and daytime habits (24 questions). Of the latter, 18 multiple-choice questions provided answers expressed as discontinuous variables on a nominal scale, 4 questions provided answers expressed as continuous variables on an interval scale, and 2 questions provided answers expressed as quality characterization on a five-point scale. The supplement includes information about lifestyle and academic progress on a four-point scale. Results: The S & DHQ could be used to study sleep problems in young medical students. The subjective sleep quality of students was as follows: excellent-29%; good-40%; satisfactory-24%; poor 6%; very poor-1%. Sleep quality is associated with academic progress (RZ 0.174; P!0.001), leisure activity (RZ0.210; P!0.001), and living conditions (RZ0.195; P!0.001). Sleep quality is not associated with students' daily (RZ0.021; PO0.05) or nightly workload (RZ0.0664; PO0.05). Daytime sleepiness poses a significant problem for students and is associated both with sleep disorders and work while studying. Conclusions: The study demonstrates that complaints about sleep problems are common in young medical students.