BACKGROUND: Melanoma incidence in the UK has doubled over two decades, yet there is conflicting evidence about factors which prompt or delay patients seeking advice. AIM: To explore patient understanding of pigmented skin lesions (moles) and skin cancer, and factors which influence seeking help in primary care. METHOD: Semi-structured interviews with forty MoleMate Trial participants, analysed using the theoretical framework of the Safer-Andersen model of Total Patient Delay. RESULTS: Patient understanding and awareness was influenced by personal, family and friends' experiences of moles, skin cancer and other cancers, knowledge of risk factors, and the lay media. The route to consulting was complex and often iterative. For lesions that people could see, detecting and appraising change was influenced by comparisons with a normal mole on themselves, a family member, friend or image. Inferring illness came about with recognition of changes (particularly size) as serious, and associated 'internal' symptoms such as pain. For lesions that people could not see, family, friends and health professionals detected and appraised changes. Deciding to seek help was often prompted by another person or triggered by rapid or multiple changes in a mole. Three of four people subsequently diagnosed with melanoma did not seek help; instead, their GP opportunistically noticed the lesion. CONCLUSIONS: Changing moles are often perceived as trivial and not signifying possible skin cancer. This study contributes to current national strategies to improve patient awareness and earlier diagnosis of cancer by highlighting factors that can trigger or act as barriers to seeking help.(ISRCTN79932379).