OBJECTIVES: The aim of this study was to evaluate sleep habits and sleep-related problems in high school adolescent students in Greece through the Athens Insomnia Scale and to assess the relation of these problems to demographic and other variables. METHODS: The Athens Insomnia Scale 5-item version (AIS-5) was administered to 713 adolescent senior high school students in the Greater Athens Area. Data such as age, sex, school records, and time spent per week in school-related and extracurricular activities were collected. RESULTS: The sample's mean sleep duration was 7.5 h, mean bedtime 00.20 a.m. and wake-up time 7.15 a.m. Total sleep time was not affected by gender, but was influenced by time spent in various activities. Sleep complaints were related to delayed sleep, onset latency and insufficient total duration of sleep. Of the respondents, 30% estimated that their sleep onset latency was markedly delayed and 30% reported that their total sleep time was markedly insufficient. Girls complained more than boys, while correlations showed that students with lower academic performance and those in second grade were more likely to have higher AIS-5 scores. CONCLUSIONS: The results show that the sleep time of high school students is dependent on practical matters such as school schedule and other activities, while sleep complaints are related to female gender, bad school performance as well as to the second grade. The difference between actual sleep time and sleep complaints should be considered when studying the sleep of adolescents. [ABSTRACT FROM AUTHOR]