Recognising one’s abilities and limits in clinical tasks is a valuable part of professionalism. This study investigated the self-ratings of problem-solving confidence of radiation therapists (RTs) in two domains: clinical scenarios and critical thinking items (CTIs). We divided the 60 participants into three groups based on post-qualification experience (PQE), and found that greater PQE was linked with higher self-rated confidence for clinical scenarios, but not for CTIs.