This paper describes the results of an experimental campaign aimed at investigating the long-term behaviour of cracked steel- and macrosynthetic- fibre reinforced concrete beams. In particular the behaviours of four beams, in terms of crack opening and deflection, were compared: two beams contained two different dosages of steel fibres and the remaining beams two different dosages of macro synthetic fibres. The tests showed huge differences in the long-term behaviour of the different types of fibre reinforced concretes.