We have made an extensive theoretical exploration of gas-phase N-alkylamino cation affinities (NAAMCA), including amino cation affinities (AMCA) and N-dimethylamino cation affinities (NDMAMCA), of neutral main-group element hydrides of groups 15–17 and periods 2–4 in the periodic table by using the G2(+)M method. Some similarities and differences are found between NAAMCA and the corresponding alkyl cation affinities (ACA) of HnX.