AM1, PM3 and SAM1 calculations have been carried out on eight compounds related to 1,8-diaminonaphthalene, five known proton sponges and three new compounds (a quinolizine, an isoquinoline and a 2,7-naphthyridine). The acceptable results obtained for the correlation between pK(a) and protonation enthalpies for the first five compounds using either the AM1 or the SAM1 method, gives confidence to the predicted high basicity (between 19 and 22 pK(a) units) for the unknown compounds.