Hydroxydicyclopentadiene (DCPD-OH) and some ester and ether derivatives were synthesized and used for the first time as ring-opening metathesis polymerization (ROMP) monomers to create cross-linked thermoset polymers with Ru-catalysts. The properties of this new family of polymers were measured mainly by means of TGA, DSC and DMA to compare them with those of polydicylopentadiene (pDCPD). The novel polymers showed thermal properties comparable to those of pDCPD; although glass transition temperatures were mainly reduced by the modifications. More importantly, tuneable physical properties, depending on the substituents attached, were obtained. Thus, a window towards many important applications is opened by making novel thermoset ROMP homopolymers and copolymers from monomers with significantly reduced odour.