The influence of extension of the aromatic core of phthalocyanines derivatives on the properties of the functionalized single walled carbon nanotubes (CNT) is studied. For this purpose the comparative study of the structural features and sensing properties of the CNT functionalized with zinc 2,9,16,23-tetra-tert-butylphthalocyanine (ZnPc) and zinc 2,11,20,29-tetra-tert-butyl-2,3-naphthalocyanine complex (ZnNc) is carried out. The adsorption of ZnPc and ZnNc molecules onto the CNT surface has been confirmed by Raman spectroscopy, SEM, and thermogravimetric analysis. It was determined that the number of ZnNc molecules anchored on the CNT walls is more than the number of ZnPc molecules. The more preferable π-π interaction of ZnNc molecules with CNT appears to be due to the bigger number of π-electrons forming naphthalocyanine aromatic system. Thin films of pristine CNT, CNT/ZnPc and CNT/ZnNc hybrids were prepared by drop casting onto interdigitated electrodes and applied as active layers to detect ammonia vapour (10-50 ppm) by measuring electrical resistance changes. It has been shown that sensor response of the CNT/ ZnNc hybrid toward ammonia vapours is lager than that of CNT/ZnPc hybrid.