meso-tetraarylporphyrins with different substituents linked either to an aryl ring or to a beta-pyrrolic position were studied by Electrospray (ESI) Tandem Mass Spectrometry (MS/MS). The electrospray mass spectra (ESI-MS) of meso-tetraarylporphyrins show the molecular ions and no significant fragmentation is noted. Structural information can be obtained by inducing fragmentation of the ions generated under ESI conditions. The product ions formed and registered in the tandem mass spectra (ESI-MS/MS) are characteristic of the chemical structure of the groups linked to the porphyrin and depend on their location. Also, the same functional group linked either to the aryl ring or to the beta-pyrrolic position yields different product ions that confirm their position. Taking into consideration the Portugal-Spain special issue of the Journal of Porphyrins and Phthalocyanines, in this highlight we analyze the work done at the University of Aveiro related to the use of mass spectrometry in the structural characterization of meso-tetraarylporphyrins with carbohydrate, nitro and amino acid groups.