Introduction: With the advent of complex treatment techniques like volumetric modulated arc therapy, there has been increasing interest in treatment planning technologies aimed at reducing planning time. One of these such technologies is auto-planning, which is an automated planning module within Pinnacle 3 . This study seeks to retrospectively evaluate the dosimetric quality of auto-planning-derived treatment plans as they compare to manual plans for intact prostate, prostate and lymph nodes, and brain treatment sites. Materials and Methods: Previous clinical plans were used to generate site-specific auto-planning templates. These templates were used to compare the 3 evaluated treatment sites. Plans were replanned using auto-planning and compared to the clinically delivered plans. For the planning target volume, the following metrics were evaluated: homogeneity index, conformity index, D 2cc ,D mean ,D 2% ,D 98%, and multiple dose fall-off parameters. For the organs at risk, D 2cc ,D mean , and organ-specific clinical metrics were evaluated. Statistical differences were evaluated using a Wilcoxon paired signed-rank test with a significance level of 0.05. Statistically significant (P < 0.05) differences were noted in organs at risk sparing. Results: For the prostate, there was as much as 6.8% reduction in bladder D mean and 23.5% reduction in penile bulb D mean . For the prostate + lymph nodes, decreases in D mean values ranging from 4.1% in the small bowel to 22.3% in the right femoral head were observed. For brain, significant improvements were observed in D max and D mean to most organs at risk. Conclusion: Our study showed improved organs at risk sparing in most organs while maintaining planning target volume coverage. Overall, auto-planning can generate plans that delivered the same target coverage as the clinical plans but offered significant reductions in mean dose to organs at risk.