A cross-sectional study was designed with high-school students. The study's objective was to establish the relationship between cannabis smoking and academic achievement, adjusted for clinically important depressive symptoms and family dysfunction. The authors quantified lifetime cannabis smoking, perception of academic achievement, clinically important depressive symptoms, and family dysfunction. It was computed crude association between cannabis smoking and academic achievement and adjusted by clinically important depressive symptoms and family dysfunction. A total of 1,462 students between 13 and 17 years participated in the research; 11.63% reported lifetime cannabis smoking; 30.78%, poor-fair academic achievement; 7.05%, clinically important depressive symptoms; and 76.06%, family dysfunction. The lifetime cannabis smoking was significantly associated with poor-fair academic achievement after adjusting for clinically important depressive symptoms and family dysfunction (OR = 1.61, 95%CI 1.16 - 2.24). In conclusion, lifetime cannabis smoking is related to poor-fair academic achievement among high-school students in Santa Marta, Colombia.