This study investigated the relationship between psychosocial factors and the decisional consideration of genetic testing of hereditary colon cancer. Attitudes and beliefs about genetic testing, anxiety and depression levels, coping style, and optimism were used as psychosocial independent variables. Sixty-two registrants (61% males and 39% females) of the Hereditary Gastrointestinal Cancer Registry of the Queen Mary Hospital in Hong Kong completed a mail survey. Mean age of the respondents was 42 years (SD = 9.92 years, range: 18-68 years). Correlational analyses and regression analyses were used to examine the relationships between the dependent and independent variables. Participants were concerned about the well-being and reactions of their significant others even more than their own well-being in their decisional consideration processes. Those who had higher perceived risks of being a mutated carrier and higher depression levels tended to emphasize more on the negative consequences of learning the test results and sharing them with relatives. Besides, those who believed that having cancer was attributable to personal (e.g., stress) rather than environmental factors considered that the negative consequences were relatively more important than the positive gains in sharing their results with relatives. Our participants tended to be relational or interdependent oriented in their decisional consideration processes related to genetic testing of colon cancer. This result is consistent with the established interdependent orientation of Chinese. Participants with higher risk perception focused more on the negative consequences of genetic testing. Psychological counseling might help these patients to cope with their concerns about being diagnosed as gene carriers after genetic testing.