Molds in wet and warm environments often attack surfaces of products made from beech and other less or moderately durable woods. This paper presents the effects of the physical modification of beech wood with a CO2 laser having a constant power output of 45 W, using eight radiation doses from 7.8 to 75 J/cm2. Variations in laser activations created a scale of color changes in surfaces of beech wood determined in the CIE L*a*b* system, ranging from an apparently unaffected to totally dark due to carbonization effects. The surfaces of beech samples modified by laser were subsequently infected with the molds Aspergillus niger and Penicillium brevicompactum, and their growth on the top surfaces of beech samples was evaluated according to the standard STN 49 0604 (1980). The modified surfaces of beech wood exposed to higher CO2 laser powerful effects (i.e., radiation doses 25 J/cm2 and more) obtained evidently higher resistance to Aspergillus niger, but their resistance to Penicillium brevicompactum changed only minimally.