In the last years, the quality control at the end of production lines has been improved in order to guarantee a high standard of products in particular with regard to aesthetics. In this paper, superficial defects of plastic products, due to the painting process, are taken into consideration. This kind of process requires very strict environmental conditions; in particular, the presence of impurities (such as dust) should be avoided in order to guarantee a high aesthetic quality of the finished product. Up to date, the quality control of plastic pieces is usually performed by human operators, so an automated process is needed in order to recognize the standardized parameters expressing the aesthetic quality of a plastic product. In particular, a system based on a vision system which can detect the irregularities of the finished object surfaces could be designed and implemented. In this way, it is also possible to quantify the degree of nonconformity of the final product by means of adequately defined parameters [1] and [2].