In this paper, a CMOS digital image sensor, which consists of A/D conversion, motion estimation circuits, and attention modules for ROI (Region of Interest) perception is presented. The functions of A/D conversion and motion estimation are implemented by 0.6 m CMOS processing circuit on chip, and attention modules are implemented off the chip as software currently. Attention modules are taken to improve limited applications of the smart image sensor. If the attention module is integrated on a smart sensor, we can use this sensor for tracking some regions of interest without outputting all pixels. The current smart image sensor responses to the changes of intensity, and uses the integration time to estimate motion. To make up for inherent property of the sensor from circuit design and extend its applications we decide to introduce some perceptive solutions to the image sensor. Attention modules for still and moving images are employed to achieve such purposes. The suggested approach also makes the smart image sensor initiate perceptive functions for such cases that motion estimation or intensity changes are not observed. Experimental results present the possibility that the smart image sensor can extract ROIs and use them when it selectively outputs pixels.