Many studies have been conducted in Africa on the use of psychoactive substances among high school students. However, few studies have examined the psychological mechanisms underlying this consumption. Grounded in self-determination theory (SDT), the present study explored the moderating role of the frustration of basic psychological needs on the relation between problematic school functioning (i.e. academic, emotional, and behavioral difficulties) and the consumption of alcohol and cannabis. The sample consisted of 367 Gabonese students (54% girls; M[subscript age] = 18.25). The results showed two direct links: behavioral difficulties positively predicted alcohol use, while emotional difficulties positively predicted cannabis use. Two moderating effects related to behavioral difficulties were also observed: (1) youths with these difficulties are more likely to drink alcohol when they perceive that their need for autonomy is frustrated, and (2) they are more likely to use cannabis when their need for relatedness is frustrated. The results of this study are discussed within SDT framework. The study's implications and limitations are also addressed.