Objective: To investigate the impact of miniscrews diameter on their primary stability. Methods: The study was conducted on 10 consecutive patients. Two different diameter miniscrews 1.3mm and 1.8mm were used in the study. The patients were divided into two groups according to the side of placement of each miniscrew. Primary stability of the miniscrews was measured using the periotest device. Results: Miniscrews of 1.8mm diameter showed a higher primary stability values than the small diameter miniscrews. Conclusions:Large diameter miniscrews can be used effectively as an absolute skeletal anchorage unit with a high primary stability.