Magnetic coherence resonance profiles, obtained at magetic field B = O in Hanle configuration were examined for Na and K atoms in different cells: evacuated glass cells and buffered, coated and uncoated. At low laser power for all cells the shape of the resonancees is Lorentzian. At power higher than about 100 mW/cm2, some narrowing around the resonance peak is observed for the Na buffered cell, while for the vacuum one the resonance shape is even more complex. Theoretical explanation is proposed for the complex resonance shape evidenced in the vacuum cells. Large resonance contrast in the K absorption at B = 0 is observed, attributed to the low rate of hyperfine optical pumping in K. The detailed investigation of the resonance profiles and contrast is of very high importance for their application.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.