Please use this link to access this publication. Abstract Purpose Patients with cancer are using cannabis for self-treatment. The reasons, experienced effects, and prevalence of use are unknown in the European general oncological population. Methods Adult patients with cancer attending outpatient oncology clinics were invited to participate in a cross-sectional survey. The questionnaire consisted of sociodemographic questions, validated scales on quality of life, neuropathy, anxiety and depression as well as questions regarding use of cannabis. Results The overall response rate was 83% (2839 patients) and 13% of patients were using or had used cannabis during their treatment. Rate of use was higher in smokers...