The goal is to generate and evaluate a simulated 4D Rb-82 PET dataset that realistically models simultaneous respiratory and cardiac motions for use to study the effects of the motions and their compensation using various gating schemes. Normal cardiac and respiratory (C&R) motions were simulated separately using the realistic 4D XCAT phantoms. The C&R motion cycles were divided into 24 and 48 equally-spaced time points, respectively. The simultaneous dual motions were modeled by 24x48 phantoms with different combinations of C&R motion phases. Almost noise-free projections of the heart, blood pool, lungs, liver, stomach, spleen, and the remaining body were simulated separately using the combined SimSET and GATE Monte Carlo simulation program which is 12 times faster than GATE alone. The projections were scaled and combined to simulate a typical Rb-82 myocardial perfusion (MP) PET patient study. The no gating, 6-frame respiratory gating only, 8-frame cardiac gating only, and simultaneous 6-frame respiratory and 8-frame cardiac gating schemes were applied. Each gated projection dataset was reconstructed using a 2D OS-EM without and with attenuation correction (AC) using an averaged and gated attenuation maps. The reconstructed images were evaluated in terms of artifactual non-uniformity in the MP polar map. Significant artifactual non-uniformity was found in the MP polar map over all gating scheme without AC. With AC, the artifactual decreases in both the anterior and inferior regions were reduced with respiratory gating. Cardiac motion alone did not cause significant artifactual non-uniformity. In addition, the combination of dual gating and AC using the gated attenuation map provided the most uniform MP polar map. We demonstrated the flexibility and utility of the 4D XCAT phantom set with simultaneous C&R motions. It is a powerful tool to study motion effects on MP PET studies and to evaluate C&R gating schemes, AC and quantitative 4D PET image reconstruction methods.