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Purpose: To investigate whether time-trends of enhanced [18 F]Fluoromethylcholine ([18 F]FCH) in lymph nodes (LN) of prostate cancer (PCa) patients can help to discriminate reactive from malignant ones, and whether single time point standardized uptake value (SUV) measurements also suffice. Procedures: 25 PCa patients with inguinal (presumed benign) and enlarged pelvic LN (presumed malignant) showing enhanced [18 F]FCH uptake at dual-phase PET-CT were analyzed. Associations between LN status (benign versus malignant) and SUVmax and SUVmeanA50, determined at 2 min (early) and 30 min (late) post injection, were assessed. We considered two time-trends of [ 18 F]FCH uptake: type A (SUV early . SUV late) and type B (SUV late ≥ SUV early). Histopathology and/or follow-up were used to confirm the assumption that LN with type A pattern are benign, and LN with type B pattern malignant. Results: Analysis of 54 nodes showed that LN status, time-trends, and 'late' (30 min p.i.) SUVmax and SUVmeanA50 parameters were strongly associated (P,0.0001). SUVmax relative difference was the best LN status predictor. All but one inguinal LN showed a decreasing [18F]FCH uptake over time (pattern A), while 95% of the pelvic nodes presented a stable or increasing uptake (pattern B) type. Conclusions: Time-trends of enhanced [18F]FCH uptake can help to characterize lymph nodes in prostate cancer patients. Single time-point SUV measurements, 30 min p.i., may be a reasonable alternative for predicting benign versus malignant status of lymph nodes, but this remains to be validated in non-enlarged pelvic lymph nodes. [ABSTRACT FROM AUTHOR]