To measure the penetration of three bonding systems for the luting of fiber glass posts in endodontically treated teeth, using confocal laser scanning microscopy (CLSM). A total of 30 maxillary incisors were shaped with the Mtwo system and filled with gutta-percha and Top Seal cement. The sample was divided into three groups (ni=10) according to the bonding system used to cement the posts: Group 1 (Prime&Bond NT and Rebilda DC with a total-etch technique); Group 2 (Futurabond DC and Rebilda DC with a dentin self-etch technique); and Group 3 (BisCem self-adhesive cement). Rhodamine B was added to the bonding systems to allow visualization by CLSM. Three 1-mm thick cross-sections were obtained of each root at a distance of 2, 5 and 8 mm from the coronal limit of the root. The specific software of the CLSM system was used to measure the percentage of the root canal perimeter showing penetration of the bonding system in the dentinal tubules, together with the maximum depth of penetration. Comparison between groups were made by Kruskal Wallis test, and comparison two by two groups with Mann-Whitney U-test. Depth of penetration of the resin tags, were distributed from greater to lesser depth as follows: BisCem > Prime&Bond NT > Futurabond DC. BisCem showed significantly greater penetration in the middle and apical thirds than the rest of the systems (906.14±67.42 and 699.27±76.26 µm, respectively). The percentage perimeter exhibiting penetration in the coronal third was significantly greater with BisCem versus Futurabond DC (56.08±7.24 and 44.38±5.23%, respectively). No significant differences were recorded in the middle and apical thirds among the three systems. BisCem resulted in greater depth of intratubular penetration at all studied levels. The percentage perimeter of the canal showing penetration was similar for all the bonding systems.