The Flash evaporated Zinc-Phthalocyanine (ZnPc) thin films were analyzed using atomic force microscope (AFM). A homogeneous distribution of crystalline domains call be observed from the image. The crystallite size increases with increase in film thickness. From the transmission spectra, the transmission is found to be decrease with increase of film thickness. The optical transition in ZnPc films is found to be direct and allowed. The RMS strain deceases with increasing film thickness and it strongly influences the band gap of the flash evaporated ZnPc thin films. The optical band gap energy is found to decrease with increase in film thickness. (c) 2005 Elsevier Ltd. All rights reserved.