Introduction: Circadian rhythms of a person's health and recovery from illness is important. The aim of this study was to examine the effect of circadian rhythms on quality of sleep and behavioral problems in primary school students.

Methods: The present study is descriptive- analytical type. The statistical population of the study were all 10-12 year old students In the fourth to sixth grade elementary school in shahrekord city in academic year of 2014- 2015 that among them 100 students were selected by multi- stage cluster random sampling method. Data gathering tools include circadian rhythms questionnaire, owens et al (2000) quality sleep quastionnaire and CSI-4 quastionnaire. The questionnaires were completed by parents of these students. Descriptive and inference statistics method multi- variable variance analysis and spss18 software were used to analyze data.

Result : The subscales hostility and defiance disorder, hyperactivity disorder, conduct disorder, generalized anxiety disorder, major depressive disorder and dysthymic between the three types of circadian rhythms(Morning, evening and intermediate) in less than (p<0.05) were significant differences. The estimate of abnormalities were higher in evening type. Also, delay the onset sleep, resistance to sleep and daytime sleepness were higher in evening types(p< 0.05).

Coclusions: Circadian rhythms impact in behavioral problems and quality sleep. Necessary steps to provide the educational needs of individuals in shaping their circadian rhythms at an early age is critical to growth.