Simultaneous 18F-FDG PET-MRI has shown promise for improved diagnostic accuracy of inflammatory cardiac diseases. However, respiratory motion and mis-registration between free-breathing 3D PET and 2D breath-held MR images remain challenges that have hindered its clinical adoption. We have recently proposed a free-breathing non-rigid motion-compensated 3D whole-heart T2-mapping that enables detection of myocardial inflammation and provides non-rigid respiratory motion fields to correct simultaneously acquired PET data in a 3T PET-MR system. Here, we perform a preliminary clinical validation of this approach in 8 patients with suspected cardiovascular disease. Good image quality with T2 values comparable to clinical 2D T2-mapping was achieved.