PURPOSE: To assess and compare the dimensions of LASIK flaps created by the Ziemer FEMTO LDV "Classic" femtosecond (FS) laser and Moria M2 microkeratome with 110-mu m head and -20 blade. METHODS: Seven hundred twenty eyes from 360 consecutive patients were enrolled in this study and divided into two groups of equal size for flap creation with the Ziemer LDV (FS laser group) and Moria M2 mechanical microkeratome (microkeratome group). Nominal flap thickness was 110 mu m for all patients and for both devices. Flap thickness was measured by Fourier-domain optical coherence tomography in 14 specified positions on each flap 1 week after surgery to analyze the regularity, uniformity, and accuracy of the two types of LASIK flaps. RESULTS: The mean deviation between achieved and attempted flap thickness was smaller in the FS laser group than in the microkeratome group. The flaps in the FS laser group were more regular and uniform, showing an almost planar configuration, whereas flaps in the microkeratome group had a meniscus shape and were significantly thicker near the flap edge. Nasal and temporal flap thickness did not differ significantly in the FS laser group, whereas in the microkeratome group, characteristic differences in temporal versus nasal flap thickness were noticed. Within the 5040 individual measurements of the 360 eyes, deviations of >20 mu m were observed in 0.73% of eyes in the FS laser group and 42.4% in the microkeratome group. CONCLUSIONS: The dimensions of flaps created by the Ziemer LDV femtosecond laser were more uniform and accurate than those created by the Moria M2 microkeratome. [J Refract Surg. 2012;28(3):189-194.] doi:10.3928/1081597X-20120208-01