The aim of the present study was to examine the effect of cardiac anisotropy on the ECG activation time imaging solutions using a cellular-automaton-heart-model-based approach. The anisotropic heart model was used in forward pacing simulation while anisotropic and isotropic heart models were used in inverse procedures, respectively. Twenty-four sites throughout the ventricles were paced and the corresponding cardiac activation sequences were inversely estimated. The inverse solutions of activation time using anisotropic or isotropic heart model were compared. The computer simulation results suggest that the cardiac anisotropy does not seem to have significant influence on the inverse estimation of activation time using the present 3D heart-model- based inverse imaging approach during single paced activation.