Summary The advent of modern treatments together with the improvement of the surgical techniques has significantly increased 5‐year survival rates of young patients with cancer. Although the deleterious effects of chemotherapy and radiation are well documented, controversies exist about the effect of cancer itself on semen parameters before treatment. We collected data on 236 patients representative of different types of cancers reoffered at our institution for sperm cryopreservation with the aim to correlate the pre‐freeze semen parameters with type of cancer, disease stage and with semen quality of 102 fertile and healthy men. The median baseline semen parameters of all our patients with cancer are placed above the 5th percentile of the World Health Organization reference value, but the type of cancer may impact the sperm parameters. In testicular tumours and in Hodgkin lymphoma, we show a semen concentration statistically lower than in the fertile population, while in patients with other cancers, there is no difference with the healthy men. We found no correlation between semen quality and disease stage. Eighty‐six per cent of our patients do not have children at the time of semen cryopreservation, and the only established clinical option for preserving fertility of these men is cryopreservation of spermatozoa.