The microhardness behaviour of binary blends comprising a styrene/butadiene star block copolymer and polystyrene homopolymer (hPS) over a wide composition range is investigated. In particular, the interrelation between the morphology, tensile properties (such as yield stress cry and the Young's modulus, E) and the microhardness H is explored. As in the case of microphase separated block copolymers and binary block copolymer blends, as reported in preceding publications, a clear deviation in the microhardness behaviour from the additivity law is observed. The lamellar block copolymer system is compared with the nanostructure of semicrystalline polymers having a lamellar morphology. A dependence of H upon PS lamellar thickness is found. For the samples with lamellar morphology the hardness value was found to correlate with the mechanical parameters obtained by uni-axial tensile testing according to: H/sigma(Y) similar to 2.2 and E/H similar to 22. (C) 2003 Elsevier Ltd. All rights reserved.