Abstract The use of steel deck slabs has proved over the years to be one of the most economic structural building systems. Despite this affirmative, mainly for various historic reasons beyond the scope of the present paper, the Brazilian construction industry has not fully exploited the considerable potential of this structural solution. The first part of this paper presents and discusses the analytical and experimental results of a wide-rib composite steel deck developed at the Structural and Materials Laboratory of PUC-Rio. The steel decks results are centred on the steel/concrete longitudinal shear ultimate limit state, load vs. slab strain curve responses and on steel deck design and detailing recommendations. The final part of the paper focuses on an innovative composite slab system made of a steel deck and a styrofoam plate, side by side, filled with reinforced concrete also developed at PUC-Rio. A parametric analysis of the steel deck profile was first performed. When an optimum steel deck profile was established, the investigation proceeded with a series of full-scale-experiments to access the system’s ultimate and serviceability limit states. The experiments also comprised the study of the concrete vs. steel deck interlocking or mechanical shear transfer devices.