Purpose Radioembolization has shown promising results in the treatment of unresectable metastatic gastrointestinal cancer to the liver, however the tumor response is unpredictable. The importance of predicting the outcome of selective internal radiotherapy (SIRT) in these patients cannot be over emphasized. This retrospective review was conducted to determine if the radionuclide uptake on SPECT can predict the outcome in these patients treated with Yttrium-90 glass microsphere radioembolization. Materials and Methods 26 patients with known history of SIRT for hepatic metastasis from GI tumors (colorectal, pancreatic etc.) were included in the study. Baseline and post-SIRT CT images (1 month, 3 months and 6 months post-SIRT) were analyzed to find out the progression free survival (PFS). Overall Survival(OS) was also calculated.The radionuclide uptake was then stratified into one of the four categories: Hypovascular tumor, Halo of activity around the tumor, peripheral activity within the tumor and Central/diffuse activity. Kaplan-Meier methods were used to estimate survival curves. Results Twenty-six patients (64% M; average age of 60 years) were included in the study. On evaluation of the SPECT characteristics, 15 pts (57.7%) had a halo of activity around the lesion, 8 pts (30.8%) demonstrated peripheral activity within the tumor itself, 2 patients (7.7%) demonstrated diffuse/central activity and only 1(3.8%) was hypovascular with no significant activity. No statistically significant correlation was demonstrated between the SPECT characteristics and OS and PFS. 17 (68%) patients demonstrated increase in the size of the target lesions after one month of SIRT, thus demonstrating progression according to the RECIST 1.1 criteria. Conclusion There is no significant correlation between the hypervascularity pattern on SPECT and overall survival. 68% of the lesions demonstrated increase in the size after one month of therapy, though many of these patients had prolonged survival; thus, RECIST 1.1 criteria may not be sufficient to access tumor progression in these patients.