Background: Substance use disorders (SUD) are serious social problems that cause physiological and psychological disorders. Adolescents and youth are known as high-risk groups for SUD. Objectives: The present study aimed to investigate the pattern, prevalence, incidence, and etiology of SUD among all students studying at the Ilam University of Medical Sciences, Ilam (Iran), during the academic year 2018 - 2019. Methods: In a cross-sectional study, a multistage random sampling method was used to select the participants. A self-administered questionnaire was used to collect data. This questionnaire was designed to collect information about the participant’s demographic data, social data, medical and behavioral data. Data were analyzed using descriptive and inferential statistics in SPSS 16 software. Results: Participants’ ages mean ± SD was 23.5 ± 3.2 years old. The incidence of substance abuse was higher among men compared to women. The main observed pattern of SUD was Marijuana among consumers. The curiosity and increased memory had the highest and lowest incidence, respectively. Conclusions: The incidence of SUD is high among Iranian students, and most of them have begun SUD in adolescence and because of curiosity. It is necessary to augment adolescents’ and young people’s awareness of the SUD and addiction consequences.