In this paper, the discharge characteristics of ac-type cylindrical discharge devices with diameters (D) in the $50{sim}400{mu}m$ range have been investigated numerically. The cylindrical devices have much lower breakdown voltages compared to the coplanar electrode structures. The breakdown voltage of the cylindrical structures increases with the decrease of diameters in $50{sim}100{mu}m$ range. In $100{sim}200{mu}m$ range, however, the breakdown voltage decreases slightly with the decrease of diameters. Also, as the diameter gets smaller, the electron heating efficiency is greatly improved.