Objective To develop and test an image fusion software(fDf,fMRI/DTI fusion) which can overlap the anatomical(T1WI images), functional MRI(fMRI) and diffusion tensor imaging( DTI) sim-ultaneously for preoperational evaluation of patients tumor. Methods fMRI with bilateral hands grasp move-ment and DTI were performed using GE 1. 5 T magnetic resonance system on 10 subjects (5 healthy volun-teers and S patients with brain tumor,of which 3 were metastases, 1 was cavernous hemangioma and 1 was gli-oma). All data were input to the personal computer and off-line postprocessing of fMRI and DTI data was per-formed using SPM5 and Volume-One software package to visualize the activated functional cortex areas and corticospinal tracts. fDf was used to import the fMRI and structural images to Volume-One to show them sim-ultaneously. Results Brain functional activation maps and diffusion tensor fiber tracking images were ob-tained in all five healthy volunteers and four patients except one who suffered from left hemiplegia. The func-tional activation maps and the fiber tracking images were successfully fused by the fDf software,where the ac-tivations areas and the white matter fiber were displayed together. The fusion images of healthy volunteers showed the hand motion areas and corresponding corticospinal tracts, while that of the patients display the re-lationship of the eloquent cortex and peritumoral fiber tracts, which were useful in guiding the treatments for the surgeons and radiotherapists. It only took hours to present the fused images to the neurosurgeons or the ra-diotherapists. Conclusions All the results confirm that the image fusion software work well for all the data.It is an easy,free and fast way to realize the image fusion. The neurosurgeon and radiotherapist consider the software were very helpful for preoperative planning.