This paper analyses the accuracy of FE (Finite Element) modelling of concrete thin slabs, reinforced with GFRP (Glass Fiber Reinforced Polymer) bars, under bending loading conditions. It considers two strategies of concrete/bar interaction approach – direct and indirect. Indirect bond approach was combined with concrete tension stiffening model, whereas the direct bond one employed plain concrete constitutive model. Apart from selection of material and bond models, FE mesh sensitivity was examined. The efficiency of both bond modelling strategies was proven for the slab of standard thickness (100 mm) failed due to concrete crushing, whereas direct bond method was shown indispensable when simulating very thin slabs (40 mm) failed due to bar debonding.