3D organic-inorganic (hybrid) perovskites have raised great technological interest over the past few years owing to their high potential in photovoltaics and optoelectronics. This is in great part due to their high light power conversion efficiencies, currently exceeding 22% . Recently, their 2D layered counterparts have gained renewed interest as, among others, they demonstrate excellent photo-stability under operating conditions and resistance to humidity and heat stress . However, these interesting properties need to be theoretically understood in order to get physical insights that shall help the engineering of improved devices. In this regard, various theoretical tools, including tight-binding models , are of particular value. Here, we present DFT based results on perovskites adopting the crystal structure of the Ruddlesden–Popper type , to understand the mechanisms that are prominent in their exciting photo-physical properties. For instance, both their electronic and dielectric properties will be discussed with particular attention on quantum and dielectric confinement effects. Thanks to the information gained, excitonic effects will be subsequently tackled.