The comparison of the effect and efficiency of three nucleating agents, a sorbitol clarifier a traditional heterogeneous nucleating agent and poly (vinylcyclohexane) showed that they modify properties in different ways and extent. PVCH is efficient already at small concentrations and increase the stiffness of iPP considerably more than the other two compounds. On the other hand, the clarifier and the traditional nucleating agent induce better optical properties even at smaller efficiency. The structure developing in the presence of three nucleating agents is also different. The sorbitol forms a network in iPP and initiates the formation of a microcrystalline structure, microspherulitic structure develops in the presence of the heterogeneous nucleating agent, while large supermolecular structure, relatively large supermolecular units form in iPP nucleated by PVCH even under the conditions of injection molding. The calculation of nucleus density by existing models and the comparison of the results to optical properties proved that haze and transparency are determined by the size of the supermolecular units of the polymer and this latter depends on nucleus density. Although the explanation needs further considerations and checking, it agrees well with the experimental results and offers an insight into the structure-property correlations of nucleated iPP product.