Recently, most European governments have attempted to reform corporate tax rules in order to favour equity financing over debt. In Italy, in particular, since 1998, the corporate tax system has deeply changed, thank to the introduction of the so-called "Visco reform". The reform innovations are an interesting experiment of a corporate taxation oriented to equity financing. The main objective of the legislator introducing the two-rate system called "Dual Income Tax System" (DIT) is to encourage the capitalisation of firms. The aim of this paper is to analyse "the optimal capital structure" which maximizes the net income of firms under different tax systems. Our model shows that two-rate systems are more neutral than one-rate systems such as the tax system existing before the Visco's reform and that prospected by Tremonti, the latter Minister of Finance.