JCOM_V1_N4_RP4 Simija Asmilin Dinsy Alphonse Journal on Computer Science 2347–6141 1 4 22 25 Cancer Detection, Image Preprocessing, Watershed Management Algorithm, Computed Tomography (CT), Contrast Enhanced (CE) Lung cancer has been the largest cause of cancer deaths. In this Computed Tomography (CT) images are used which can be more efficient than X-ray. Hence, a lung cancer detection system using image processing is used to classify the presence of lung cancer in CT images. In this study MATLAB have been used. The process such as image preprocessing, Masking, Equalization and classifications are performed. To get more accurate results the sensitivity method is used. December 2013 - February 2014 Copyright © 2014 i-manager publications. All rights reserved. i-manager Publications http://www.imanagerpublications.com/Article.aspx?ArticleId=2715