Understanding the interactions between a drug and its target protein is crucial in order to guide drug discovery. Indeed, this process involves many parameters that need to be analyzed separately to better understand their effects.We propose two new approaches to observe protein/ligand relationships. The first focuses on the comparison of cavities formed by binding sites that can accommodate a small molecule. This method allows to infer the function of a protein but also to predict the accessibility of a binding site for a drug. The second method focuses on the comparison of non-covalent interactions made between the protein and the ligand to improve the selection of potentially active molecules in virtual screening, and to find new molecular fragments, structurally different but sharing the same mode of interaction.