Two isomeric Schiff bases, HL (1) = 1-[(2-dimethylamino-ethylimino)-methyl]-naphthalen-2-ol and HL (2) = 1-[(2-ethylamino-ethylimino)-methyl]-naphthalen-2-ol, have been used to prepare copper(II) complexes in presence of thiocyanate. HL (1) forms a mononuclear complex [Cu(L (1) )NCS] with terminal thiocyanate, whereas the isomeric Schiff base HL (2) , which is capable of hydrogen bonding, gives a dimeric complex, [Cu-2 (L (2) ) (2)(NCS)(2)], with double mu-1,1-NCS bridges. Both complexes are characterized by physico-chemical and spectroscopic methods as well as by single crystal X-ray diffraction studies.