Introduction: Little is known about the factors that influence family physician (FP) participation in continuing professional development (CPD) programs in shared decision making (SDM). We sought to identify the factors that motivate FPs to participate in DECISION+, a CPD program in SDM. Methods: In 2007-2008, we collected data from 39 FPs who participated in a pilot randomized trial of DECISION+. In 2010, we collected data again from 11 of those participants and from 12 new subjects. Based on the theory of planned behavior, our questionnaire assessed FPs' intentions to participate in a CPD program in SDM and evaluated FPs' attitudes, subjective norms and perceived behavioral control. We also conducted 4 focus groups to explore FPs' salient beliefs. Results: In 2010, FPs' mean intention to participate in a CPD program in SDM was relatively strong (2.6 plus or minus 0.5 on a scale from -3 = "strongly disagree" to +3 = "strongly agree"). Affective attitude was the only factor significantly associated with intention (r = 0.51, p = 0.04). FPs identified the attractions of participating in a CPD program in SDM as (1) its interest, (2) the pleasure of learning, and (3) professional stimulation. Facilitators of their participation were (1) a relevant clinical topic, (2) an interactive program, (3) an accessible program, and (4) decision support tools. Discussion: To attract FPs to a CPD program in SDM, CPD developers should make the program interesting, enjoyable, and professionally stimulating. They should choose a clinically relevant topic, ensure that the program is interactive and accessible, and include decision support tools.