The behavioural and psychological impact of genetic testing for lung cancer susceptibility was examined among smokers (N = 61) who were randomly allocated to a GSTM1 genetic testing group (with GSTM1-missing or GSTM1-present result) or no-test control group. The GSTM1-missing (higher risk) group reported greater motivation to quit smoking, and both genetic testing groups reported lower depression than the control group at one-week follow-up (p < .05 for all). Differences were not significant at two months follow-up. This study indicates the feasibility of much-needed research into the risks and benefits for individuals of emerging lifestyle-related genetic susceptibility tests.