Background: Measurement of social cognitive variables is often restricted to long-term and health-related outcomes. A more comprehensive measurement of cognitive determinants would enable evidence-based design of health behavior interventions with a focus on the most relevant targets. The purpose of this study was to examine the relative impact of different social cognitive determinants on fruit and vegetable (FV) and fast food consumption. Methods: Finnish male conscripts (N = 855, age M = 20) filled in questionnaires on social cognitive factors when entering the military service, and on food consumption frequency after two months. The data were analysed using structural equation modeling. Results: Physical well-being expectation and bad taste expectation were most strongly related to both FV and fat avoidance intentions. Perceived weight gain risk predicted fat avoidance intention, whereas perceived risk for other health problems predicted FV intention. Social self-efficacy was associated with FV intention only. Consumption of both FV and fast food was predicted by action planning and intention. Conclusions: A more careful evaluation of subtypes of social cognitions sheds light on the specific content behind motivation. Such understanding might help in designing more effective intervention messages.