The preferred and actual participation roles during decision making have been studied over the past two decades; however, there is a lack of evidence on the degree of match between patients' preferred and actual participation roles during decision making. A systematic review was carried out to identify published studies that examined preferred and actual participation roles and the match between preferred and actual roles in decision making among patients with cancer. PubMed (1966 to January 2009), PsycINFO (1967 to January 2009), and CINAHL (1982 to January 2009) databases were searched to access relevant medical, psychological, and nursing literature. Twenty-two studies involving patients with breast, prostate, colorectal, lung, gynecological, and other cancers showed discrepancies between preferred and actual roles in decision making. These groups of patients wanted a more shared or an active role versus a less passive role. Across all cancer types, patients wanted more participation than what actually occurred. Research to date documents a pervasive mismatch between patients' preferred and actual roles during decision making. Yet, there is lack of innovative interventions that can potentially increase matching of patients' preferred and actual role during decision making. Role preferences are dynamic and vary greatly during decision making, requiring regular clinical assessment to meet patients' expectations and improve satisfaction with treatment decisions.