The aim of the study was to confirm the mediation effects of the task-specific self-efficacy on the relationship between the general self-efficacy and intention and planning considering treatment. The study comprised 265 subjects, of which 165 were post-mastectomy women and 100 patients hospitalized due to acute coronary syndrome (ACS). The variables were assessed using the Generalized Self-Efficacy Scale (GSES) and tools developed to examine the context of treatment. The data were analyzed using the bootstrapping procedure. The results confirmed the indirect effects of task-specific self-efficacy, both in women making a decision to undergo breast reconstruction, and in patients after ACS formulating intention to change risk behaviours. As smoking was considered to be a moderator in the post-ACS group, the obtained associations were observed only among the patients declaring quitting smoking. In view of the fact that taskspecific self-efficacy is susceptible to context (e.g. it may depend on quitting smoking), it is useful to assess it in order to increase treatment effectiveness.