To determine the clinical and radiographic effectiveness of CTZ paste compared with modified Guedes Pinto (GPM) used in pulp necrosis in children from 3 to 6 years of age of the Pediatric Dentistry Service of the Hipólito Unánue National Hospital. Experimental, longitudinal and prospective study. Forty-eight children aged 3 to 6 years were evaluated, obtaining 56 deciduous teeth with a diagnosis of pulp necrosis. Pulpectomy treatment was performed and the distribution of the groups was randomized. Twenty-seven teeth were obturated with CTZ paste and 29 teeth with GPM paste. To determine the effectiveness of the pastes, clinical and radiographic controls were performed at two, eight and sixteen weeks. The data were processed through the SPSS v.15.0 statistical program using Fisher's chi-square and exact tests, at a confidence level of 95%. Clinically, the decrease in symptoms of both pastes was observed at two, eight and sixteen weeks with no significant differences (p>0.05). Radiographically, significant differences (p<0.001) were found at two weeks in both groups, showing success of the CTZ paste.