Abstract:Background: Contemporary threats to adolescents' health are primarily the consequence of risk behaviors and their related adverse outcomes. Identifying factors associated with adolescents' risk behaviors is critical for developing effective prevention strategies. A number of risk factors have been identified, including familial environment; however, to the investigator's best knowledge, there have been only one previous study of possible differential vulnerabilities of in-school adolescents to risky sex in reference to parental influences and living arrangements in Ethiopia. Objective: To assess and compare sexual risk behaviours of preparatory students in West Gojam zone, in reference to their living arrangements Methodology: A comparative cross-sectional study was done in ten preparatory schools; West Gojam zone, Amhara National Regional State, Ethiopia. The study participants were selected based on probability proportional to size. A total of 314 students [104 living permanently in the corresponding towns and 210 not], were included in the study. Result: Seventy three (23.2%) respondents had ever had sexual intercourse with an individual of the opposite sex. Disaggregated by sex, 55 (25.0%) of males had had sex compared to 18 (19.4%) of females. Twenty two students (33.3%) reported having had two or more sexual partners in their lifetime (range 1-7, average1.56). In the logistic regression analyses, controlling for observed covariates, age more than 20 years [OR= 2.85; 95%CI= 1.07 to 7.59], having peer pressure to have sex [OR= 4.43; 95%CI= 2.02 to 9.69] and perceived family connectedness [OR= 0.96; 95%CI= 0.92 to 0.99] continued to be significantly and independently associated with sexual activity Conclusion: A greater sense of connectedness to parents decreases the likelihood of sexual activity regardless of living arrangement, Parental monitoring, gender, khat and alcohol consumption, and parental education. Students with peer pressure to have sex are more likely to initiate sexual intercourse.