Recurrence of prostate cancer after radical prostatectomy is a common event. Salvage radiation therapy (RT) is the mainstay of treatment in cases with recurrence defined as PSA failure, offering the chance of cure. Multiple studies showed that the lower the PSA level at the beginning of salvage RT, the better the treatment outcome. There is evidence that higher radiation doses are associated with improved PSA relapse free rates. Four different recurrence patterns exist: 1) local recurrence in the prostatectomy bed only; 2) loco-regional metastases in the pelvic lymph nodes; 3) distant metastases (most commonly nodal or osseous); 4) a combination of local and distant recurrence. Modern functional imaging modalities like magnetic resonance imaging (MRI) and choline-PET/CT offer additional information to clinical and therapeutic variables and provide high accuracy depending on the level of PSA recurrence and PSA kinetics. These image modalities are valuable tools that can be used for gross tumor volume (GTV) definition in the RT-planning process in the salvage RT setting and guide interdisciplinary salvage therapy strategies in case of locoregional relapse. We discuss the impact of MRI and choline-PET/CT in the salvage setting from the radiation-oncologist point of view.