Objective: To evaluate the incremental efficacy of a Short Message Service (SMS) combined with a brief video intervention in increasing the effects of a health education intervention for cervical cancer prevention, over and beyond a video-alone intervention, with respect to key determinants of health behaviour change--knowledge, motivation and intention. Methodology: Quasi-experimental study design, comparing three conditions--control group, video intervention group and SMS + video intervention group. Participants were 144 Portuguese female college students allocated into one of the three experimental conditions. The effects of the health education interventions were assessed using a theoretically based multidimensional cancer prevention questionnaire. Data were collected at baseline and post-test. Results: Interventions significantly increased the key predictors of adhesion to cancer preventive behaviours. SMS contributed to increases in the expected directions. Evidence of the superiority in efficacy of the combined intervention (SMS + video) over the video-alone intervention was found for cervical cancer screening. Interventions were not as effective in improving intentions and more complex preventive practices such as sexual behaviour as they were in improving knowledge. Conclusion: Results are encouraging in that cervical cancer prevention knowledge and motivation appear modifiable via a one-session video preventive intervention. If, however, the development of intentions is an important predictor of effective behaviour change, study findings point to the added importance of an SMS-based strategy for improving specific cancer preventive behaviours. Findings reinforce the need for specific and tailored health education interventions according to the various determinants of behaviour change, as well as to the particular target behaviour with respect to cervical cancer prevention.