In recent years, breast cancers have been diagnosed by various imaging modalities. One of those imaging methods is Diffuse Optical Tomography (DOT). Currently, in imaging systems, image processing methods which is the next stage when digital images are obtained, are important task for the images to be well formed. This study was applied interpolation methods, one of the image processing methods to make the images better, to protect the details and also enlargement and resizing without distortion. In this study, we used three- dimensional (3D) images generated by measurements from breast phantom with the DOT system. Four interpolation methods; nearest neighbor interpolation, bilinear interpolation, bicubic interpolation and cubic spline interpolation are applied to the 3D images. The signal- tonoise ratios (SNR) were calculated to determine the quality of the images after the interpolation methods applied. In order to evaluate the images obtained from different directions and angles, two dimensional (2D) and three dimensional (3D) images were created and their advantages and disadvantages were compared. After interpolation methods were applied, signal- to- noise ratios (SNR) were compared and tested for compatibility with our system and it was determined that the most appropriate method was the cubic spline interpolation.