Breast cancer is the most common cancer in women worldwide. Computer-aided diagnosis (CAD) has been defined as a diagnosis made by a radiologist who uses the output of a computer analysis of the images when making his or her interpretation. In this Book, first a comparison between two image enhancement techniques is done to enhance the peripheral area of the breast region. Then a CAD system is developed for classifying abnormal lesions in mammograms to differentiate between normal regions and mass lesions. The obtained results show acceptable sensitivity and specificity for the system. After that a comparison between two pectoral muscle segmentation techniques is done. Finally we test the 2D auto-regressive modeling in classification of microcalcification.