(eng): The fluorescence in-situ hybridization (FISH) belongs to the most common cytogenetic methods and is widely applied in routine clinical genetic diagnostics. We are paying attention to FISH analysis of chromosomal aneuploidies – the deviations from chromosomal number. Such analysis is based on evaluation of up to several hundreds of microscopic images. Computer support for this process includes using methods of image processing and data mining. In this paper, we focus on the image processing part in more detail: first, the properties of FISH images are reviewed, then, the processing flow is outlined. Our aim is to find the interphase and metaphase nuclei and the hybridization signals contained in the image. A simple method using the raw and central moments of detected objects as measures to distinguish between the two types of nuclei is proposed.