Presented paper refers to analysis of properties of different gray cast irons (with flake and spheroidal graphite) with ferrite, ferrite-pearlite, pearlite as well as unstable (for example bainite, maternsite) matrixes in the aspects of influence of these properties on the final laser heat treatment effect. The analysis showed that it is possible to expect essential differences in surface layer between cast irons with different graphite shape. It was shown that the range of changes caused by laser heat treatment performed in the same conditions for cast irons with spheroidal graphite can be several times larger than for cast irons with flake graphite. Consequently, to achieve the same effects it is necessary to apply higher laser beam fluence for flake cast irons than spheroidal cast irons.