Purpose: To compare the adaptation of conventional cast posts and cores to digitally milled counterparts in round and oval-shaped canals and to evaluate the retention of the milled posts. Materials and Methods: One cast post and one milled post were fabricated for each of the 26 selected teeth, which had either round or oval-shaped canals. The apical gap was evaluated with radiography, and coronal adaptation was evaluated by weighing the silicon wash trapped between the post and canal wall and also by comparing the volumes of the stereolithographic models. The milled posts were cemented with self-curing glass-ionomer, and the pullout test was performed to evaluate retention. A two-way analysis of variance and independent t test were used for statistical analyses, with α = .05. Results: Conventional cast posts and cores revealed significantly higher coronal adaptation and less apical gap than the milled groups (P .001), irrespective of the type of canal. Within the milled groups, there was no significant difference between the coronal adaptation of posts in the round and oval canals. On the contrary, the apical gap of milled posts was the least in the round canals (P = .024). The pull-out test revealed no statistically significant difference between the milled posts in the round and oval canals (P = .0864). Conclusion: Conventional cast posts and cores revealed significantly better adaptation compared to the milled group. However, the adequate adaptation of the milled posts to the coronal portions of the canals provided tolerable retention. Nevertheless, clinicians should be cautious with the application of the scan posts, particularly in oval canals, as they could result in a large apical gap.