One of the most significant characteristics of JPEG2000, the emerging still image standards, is the ROI (Region of Interest) coding. JPEG2000 provides a number of ROI coding mechanisms and ROI parameters. To apply them to an application, it must select the applicable values. In this paper, we evaluate how the ROI coding mechanisms and the ROI parameters influencing JPEG2000 quality affect the ROI quality and the whole image quality. The ROI coding mechanisms are Maxshift and Implicit, and the parameters are tile size and ROI size, codeblock size, number of DWT decomposition levels and ROI importance. The bigger the tile size, the better the quality. The bigger the ROI size, the ROI importance and the number of DWT decomposition levels, the worse the quality. In code block 32X32 of Maxshift and Implicit, it has the best quality.