The aim of this study was to explore experiences of participation in treatment planning decisions from the perspective of patients recently treated for colorectal cancer. Ten patients were purposively selected and interviewed. Constant comparative analysis, the core concept of grounded theory, was used. The dimensions were developed and organized into the main theme of 'compliant participation in serious decisions', which was composed of the two variations: complying with participation; and complying without participation. Complying with participation was characterized by feelings of self-confidence and self-competence and by open dialogue between the participants, significant others and the physician. Complying without participation was characterized by participants' feelings of uncertainty and distress, and of being rushed into submitting to decisions without having time to reflect on the information provided or the opportunity to influence the treatment and care process. To participate (or choosing not to participate) builds on open and affirming dialogue, information and knowledge about the illness. Patient participation in treatment and care decision making is interpreted as a health promoting way of coping with illness.