A method and system for differentiating a vessel and a nodule within an image. The method and system first identifies a complex object in the image and then identifies portions of the complex object as a vessel or a nodule using a distance transform based method. A simplex object is identified in the image and the simplex object is identified as a vessel or a nodule using compactness values. Complex objects are analyzed using features in a distance transform map to identify a) nodule parts and b) vessels that are attached to or pass through the nodule parts.