Background: The present study aimed to assess modifiable risk factors in patients at high risk for colorectal cancer (CRC) and their experience of lifestyle advice. Methods: A questionnaire study was conducted in high-risk CRC patients attending for surveillance colonoscopy. Current lifestyle behaviours [smoking, alcohol, diet (fruit and vegetables, wholegrains, red meat, processed meat), physical activity and bodyweight] related to CRC were ascertained, and experience on receiving, seeking and desire for advice was queried. Results: In total, 385 study invitations were sent and 208 (54%) questionnaires were returned. The majority of participants (72%) were estimated to have a body mass index beyond the healthy range, 89% achieved a fibre score indicative of a low plant-based diet and 91% reported eating processed meat. Overall, 36% were achieving at least four recommendations and 2% were adhering to all recommendations examined. The main area in which participants reported receiving advice on was body weight (33%) and 31% reported that they had personally sought information on this topic, although the data suggest that 72% of people may benefit from such guidance. Fewer participants reported receiving (18–26%) and seeking (15–17%) dietary advice on fruits, vegetables and wholegrains. Many participants said they would find lifestyle information useful, notably in relation to body fatness (43%) and physical activity (38%). Conclusions: The development of a process for supporting lifestyle change in this patient group, comprising individuals who are already engaging in positive health practices (regular colonoscopy surveillance), could usefully be identified and tested.