Objective: Consumption of excess added sugar in the form of sugar-sweetened beverages (SSBs) 3 contributes to a wide range of health concerns in adolescents. Identification of modifiable 4 determinants of SSB consumption based on behavioral theory may inform development of interventions aimed at reducing SSB consumption. The aim of the current study was to test the 6 efficacy of an extended version of the health action process approach to predict adolescent SSB 7 consumption. 8 Methods: Using a prospective design, adolescent students (N = 450) self-reported their outcome 9 expectancies, perceived behavioral control, intentions, habit, action, maintenance, and recovery 10 self-efficacy, action and coping planning, perceived affordability, and past behavior with respect to 11 SSB consumption. One month later, participants self-reported their SSB consumption. 12 Results: A structural equation model revealed significant direct effects of action self-efficacy, 13 outcome expectancies, and perceived behavioral control on intentions to reduce SSB consumption. 14 Significant direct effects of action self-efficacy on maintenance self-efficacy, and maintenance self-15 efficacy on recovery self-efficacy, were also identified. There were significant direct effects of 16 intentions and maintenance self-efficacy on action and coping planning. Only intentions and 17 perceived affordability had significant direct effects on SSB consumption. There were also indirect 18 effects of outcome expectancy and perceived behavioral control on SSB consumption mediated by 19 intentions. Inclusion of past behavior attenuated model effects, with past behavior the only 20 remaining predictor of SSB consumption. 21 Conclusions: Findings indicate that adolescent SSB consumption is predicted by intentions and 22 perceived affordability, but effects were extinguished by the inclusion of past behavior. The 23 pervasive effects of past behavior point to the importance of identifying potential mediators of past 24 behavior in future research, and that interventions targeting non-conscious rather than intentional 25 processes may be most effective in reducing SSB consumption.