The aim of this paper is to compare the properties of concrete slabs when two types of fibres are added. Steel fibres and polypropylene fibres in the volumetric ratio of 0.5% and 1.0% were added to four slab specimens. The fifth specimen had no fibres and acted as a control specimen. The dimensions of the slab specimens were 820×820×80 mm and were supported by four rollers at their edges. A displacement controlled point load was applied at the centre of the slabs. The ductilities of the tested slabs were calculated and compared so as their load carrying capacities. Comparison was also made with theoretical calculations in order to determine the load-deflection curves of the tested slabs. Results of the experimental programme were compared with theoretical predictions. Based on the results of the experimental programme, it can be concluded that the addition of 1% by volume steel fibres had the best effect on the ductility of the slabs.