Abstract Aims Glioblastoma (GBM) is currently an incurable malignancy with a very poor prognosis for the majority of patients. Many patients undergo debulking surgery, radiotherapy and chemotherapy however therapeutic options are limited, and this can lead to patients sourcing their own treatments. There is some evidence that cannabinoids have the effect of inhibiting GBM tumour growth through a variety of pathways, some of which include CB2 cannabinoid receptor pathway activation. We undertook a patient questionnaire to understand what alternative therapies patients are accessing and why, with a focus on cannabinoid use. Method We undertook a prospective observational questionnaire based qualitative study of 50 … consecutive patients undergoing treatment for glioblastoma at our centre. Results 43 patients responded to our questionnaire. 33% of patients were taking some kind of supplementary therapy with 25% taking cannabis derivatives, mainly CBD oil. There were no clear discriminators amongst our cohort including age or sex when considering the likelihood of taking cannabis derivatives. 6 out of 11 (55%) patients taking cannabis derivatives reported some positive effects with improved sleep and general wellbeing being most commonly reported. Patients reported spending between £10-£300 per month with an average of £42 per month. Cannabis products were obtained via the internet or from friends. Conclusion This small cohort of patients indicates that a significant proportion of glioblastoma patients investigate and use alternative therapies, in particular cannabis oil. NICE guidance for clinicians simply notes there is insufficient evidence to support the use of cannabis oil in the treatment of this disease. Given the publicity and interest in the utility of cannabis oil to treat cancers this leaves patients to research the use of these agents without access to robust clinical data to guide their use or indeed to conclude they are not beneficial. The accessing of these compounds, potentially by a sizeable number of patients, leaves them vulnerable to unregulated perhaps unscrupulous drug sources. This small study has further highlighted the unmet need for information and guidance on supplementary treatments for glioma patients and this poses a challenge to all those treating this group of patients to answer a question our patients are clearly wanting answered.