The stellar metallicity influences the occurrence of giant and small hot exoplanets. However, the role of elements other than iron on planetary formation is still unclear. In this talk, I will discuss the relations between the abundances of 13 chemical elements (Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, and Cu) for a sample of 561 Kepler exoplanet-hosting stars and the radii and orbital periods of their planets. These possible connections are investigated through comparisons between stars that host different planetary systems. I will also discuss the role of alpha elements in the formation of giant planets and examine the depletion of refractory elements in the Sun. The analysis of 25 solar twins in our sample suggests that this chemical peculiarity might be caused by processes other than planetary formation.