Slim-floor structures combine the advantages of prefabricated slab elements with steel-frame construction and lead to economic building solutions fulfilling the demands of modern architecture in combination with transparent structural envelopes without intervening columns as well as implicit flexibility for sustainable construction. Over past years, new slim-floor solutions have been developed to broaden the market for composite structures when compared with conventional concrete flat slabs. However, due to the shallow depth of composite slim-floor girders, their structural response, especially their deflection behaviour, differs from normal composite girders. The concrete is already in the cracked condition under service loads in regions of sagging bending moments. The contribution of the concrete chord to the effective moment of inertia Ii,0 of the composite cross-section and the bending moment Mc in the concrete chord are not negligible for the total loadbearing capacity of the composite section. These two effects are not normally considered when calculating the deflections of composite girders based on the effective width given in codes such as EN 1994-1-1 [1]. Therefore, the following paper will show different methods for calculating the deflection of these shallow types of composite girder.