Recently, not only still pictures but also moving pictures are displayed on the PDAs or cellular phones. When we take a look such pictures, the picture quality seems to be better than those on the CRTs or the large LCDs. In order to clarify the reason, we have investigated the relationship between the subjective quality of different size of pictures with keeping the viewing distance 6H. After three kinds of pictures (Girl, Mandrill, Milkdrop) are subjectively tested, the MOS using the small sized pictures with several distortions is better than that of the middle and large sized pictures by the psychophysical factors. In this paper, after discussing the effect of picture size on the MOS, we show the experimental results obtained by subjective evaluation with 20 observers. And, the relationship between the MOS and the Weighted SNR compensated by the subjective spatial frequency are given.