Clinicians should looking for techniques that helps to early diagnosis of cancer, because early cancer detectionis critical to increase survival and cost effectiveness of treatment, and as a result decrease mortality rate. Medicalimages are the most important tools to provide assistance. However, medical images have some limitations foroptimal detection of some neoplasias, originating either from the imaging techniques themselves, or from humanvisual or intellectual capacity. Image processing techniques are allowing earlier detection of abnormalities andtreatment monitoring. Because the time is a very important factor in cancer treatment, especially in cancerssuch as the lung and breast, imaging techniques are used to accelerate diagnosis more than with other cancers.In this paper, we outline experience in use of image processing techniques for lung and breast cancer diagnosis.Looking at the experience gained will help specialists to choose the appropriate technique for optimization ofdiagnosis through medical imaging.