The effect of different types of projecting walls attached to a pile-restrained U-shaped Oscillating Water Column (U-OWC) integrated with Π-breakwater on its hydrodynamic performance is analysed using Boundary Element Method (BEM). Three different types of projecting walls, such as (i) straight, (ii) inclined, and (iii) curved projecting walls are investigated. The theoretical maximum efficiency, radiation susceptance and conductance coefficients, reflection, transmission and dissipation coefficients and horizontal wave force coefficient on the top wall of the U-OWC as a function of the non-dimensional wavenumber are investigated. Geometrical variations are made in the projecting walls as well as the U-OWC relative chamber draft and their effect on the hydrodynamic performance is evaluated. The study reveals that attaching the projecting wall to the device improves its energy conversion efficiency in the long wave regime, whereas for shorter waves, the device with no projecting walls preforms better. The sloshing resonance mode occurring for high frequency waves is unaffected by the type of projecting wall since it is influenced by the internal chamber size and geometry. For any type of projecting wall, the chamber draft being too short leads to inadequate volume of water compressing the air, and a draft too big leads to flow separation inside the chamber, thereby resulting in poorer energy conversion efficiency. The wave force on the top wall is 26% lesser in absence of a projecting wall in the long wave as well as short wave regimes. The critical wavenumber is observed where the wave force is zero irrespective of the projecting wall configuration. The present numerical investigation will add to the knowledge domain of different types of projecting walls attached to OWC breakwater integrated devices.