Objectives: The aim of the present study was to determine the correlation between the thickness of both cortical bone thickness, total bone thickness and the primary stability of mini-implants. Methods: Twenty-six mini-screws (Absoanchor) were inserted into the buccal alveolar bone between the roots of the second premolar and first molar on the right and left side of the patient. The mobility of the mini-screws was clinically assessed using the periotest device and the buccal cortical bone thickness of the maxilla was measured on the right and left side in the inter-radicular area between the second premolar and first molar at the site of the miniscrew insertion. The patient’s head was oriented in all 3 spatial planes by adjusting the Frankfort plane horizontal and the orbital plane parallel to the floor. Results: There was a statistical significant differences between mean measurements of the cortical bone thickness penetrated by the mini-screw and the negative stability scores. (P=0.03) Conclusions: There was a weak correlation between the primary stability of the mini-screw and the cortical bone thickness. However, a minimum thickness of 1.0 mm cortical bone thickness is necessary for adequate stability. keywords miniscrews - stability - cortical bone thickness)