The use of c.w. laser cutting of mild steel and aluminum alloys was already been investigated. As others authors already pointed out, a converse proportion relation between thickness of material subjected to the cutting and speed of travel of the material itself takes place. In this work, refering to the previously obtained experimental data, we made some remarks on the above mentioned relation, in order to find a parameter which would be able to give useful instructions on the machinability of a fixed material by laser beam. In particular, we examined the effects on the above mentioned relation of three gases (Helium, Nitrogen, Oxygen) for different source power levels and on three kinds of materials (Aluminum alloy, Stainless steel, Mild steel). The law of correlation between thickness and speed was reviewed by some illustrative hypoteses. The obtained results seem to provide useful directions on the possibility to point out a technological parameter which could provide to laser systems consumers some information on optimization of processing conditions, by varying the maximum power of the source, the speed, the thickness, and the kind of material.