Objective: Establish an explanatory model through latent variables analysis of tobacco consumption based on al- cohol consumption and alcohol consumption based on attitudes towards consumption in a sample of university students in Ecuador. Method: Descriptive correlational and explanatory design using SEM (Structural Equation Mo- deling) techniques. Participants: 546 students (69.2% women) aged between 17 and 41 years old (M= 21.3 years old; SD= 2.6), from four universities (45.1% public ones) in two cities of Ecuador. Results: The predominance of alcohol consumption is high; the prevalence of tobacco consumption is low, and attitudes towards alcohol consumption are ambivalent. Alcohol attitudes predict alcohol consumption (R2= .57) and alcohol consumption predicts tobacco consumption (R2= .26). Attitudes and consumption provide an explanatory model for tobacco consumption with ꭓ2= 662.59; p< .001; df= 480; ꭓ2/gl= 1.4; CFI= .95; TLI= .94; SRMR= .049; RMSEA= .026 [.021 - .031]. Conclusions: The study of attitudes and consumption behaviors are important for a better understanding about alcohol and tobacco consumption in university students.