The article presents test results concerning the CO₂ and Yb:YAG laser welding of thin-walled T-joints made of steel X5CrNi18-10 (steel 304), X6CrNi18-10 (steel 304H) and X15CrNiSi25-21 (steel 310) selected as stainless steels potentially useful in the production of ribbed pipes (finned tubes) intended for operation in boilers of supercritical parameters. Welding tests were performed using two different laser sources, i.e. a CO₂ gas laser and a Yb:YAG solid state laser. The tests involved the determination of the appropriate angle of laser beam insertion into the interface of sheets, enabling the obtainment of properly shaped welds. Non-destructive tests classified the joints as representing quality level B in accordance with standard 13919-1. Selected joints were tested for the distribution of alloying constituents in the joint area. It was ascertained that laser welding made it possible to maintain the uniform distribution of alloying constituents without their significant depletion in the weld area. The tests were financed using the funds of project PBS1/A5/13/2012.