Using experiments and numerical simulations, we investigate the dewetting of thin liquid films on chemically patterned substrates. The patterns consist of long and narrow hydrophobic stripes, separated by larger hydrophilic domains. We characterize the morphology and dynamics of the dewetting front starting from an initially present dry-spot. Moreover, we study the distortion of the liquid film on the adjacent hydrophilic domains as a function of film thickness, hydrophobic contact angle and pattern dimensions. Implications of our results on the solution processing of organic electronic devices on chemically patterned surfaces are discussed.