Introduction: Prostate cancer has one of the highest incidences in the world, with good curative treatment options like radiotherapy and radical prostatectomy. Unfortunately, about 30% of the patients initially treated with curative intent will develop a recurrence and need adjuvant treatment. Five randomized trials covered the role of postoperative radiotherapy after radical prostatectomy, but there is still a lot of debate about which patients should receive postoperative radiotherapy. Areas covered: This review will give an overview on the available literature concerning post-operative radiotherapy following radical prostatectomy with an emphasis on the five randomized trials. Also, new imaging techniques like prostate-specific membrane antigen positron emission tomography (PSMA-PET) and multiparametric magnetic resonance imaging (mp-MRI) and the development of biomarkers like genomic classifiers will be discussed in the search for an improved selection of patients who will benefit from postoperative radiotherapy following radical prostatectomy. With new treatment techniques like Intensity Modulated Radiotherapy, toxicity profiles will be kept low. Expert commentary: Patients with biochemical recurrence following radical prostatectomy with an early rise in prostate-specific antigen (PSA) will benefit most from postoperative radiotherapy. In this way, patients with only high risk pathological features can avoid unnecessary treatment and toxicity, and early intervention in progressing patients would not compromise the outcome.