To further develop tailored interventions, their working mechanisms must be identified. In the present study, three tailored messages that each contained one potential working mechanism--personalization, adaptation or feedback--were compared with a standard information condition. Two hundred and two students who smoked tobacco daily were randomly divided over four conditions. After the computer pre-test questionnaire, they read the information in their condition and filled in the immediate post-test. After 4 months, they were sent a follow-up questionnaire assessing their quitting activity. The data show that personalization (44.5%) and feedback (48.7%), but not adaptation (28.6%), led to significantly more quitting activity after 4 months than did the standard information (22.9%). Moreover, the effect of condition on quitting activity was completely mediated by individuals' evaluations of the tailoring.