Background Age increases the risk of cancer and ageing processes affect treatment decisions. The aim of this study was to recognize geriatric syndromes and to evaluate the G8 screening tool for identifying patients who could benefit from comprehensive geriatric assessment. Methods The geriatric oncology project started in autumn 2018 at the oncological department of Tampere University Hospital. In the pilot study, all patients aged ≥ 75 years who were referred for consideration of medical cancer treatment were screened using the G8 screening tool by phone. Patients with abnormal G8 scores underwent comprehensive geriatric assessment. The prevalence of geriatric syndromes was compared to patients treated before the pilot study. Results Of the 101 patients screened, 69 had abnormal G8 scores and 50 underwent geriatric evaluation. Dependency in daily activities was common (ADL 41%, IADL 65%). The most common geriatric syndromes were functional decline (56% had sit-to-stand test scores below reference values) and malnutrition (44%). In the previous examinations, many geriatric syndromes had gone unrecognized or unrecorded. Conclusions Geriatric syndromes should be considered when planning cancer treatment for older patients.