Introduccion: el objetivo del estudio fue determinar y comparar cefalometricamente la variacion de la dimension vertical dentoalveolar posterior en pacientes tratados ortodoncicamente con y sin extracciones de primeros bicuspides en maloclusiones clases I y II y establecer su relacion con el indicador de displasia anteroposterior (APDI). Metodos: 76 pacientes de la Fundacion CIEO, entre 22 y 45 anos, con TeleRx lateral de craneo pre- (T1) y postratamiento (T2) de ortodoncia, clasificados esqueleticamente (APDI) y tipo de tratamiento hecho, independientemente del sexo, conformando cuatro grupos: clase I con exodoncias y sin exodoncias, clase II con exodoncias y sin exodoncias. La dimension vertical dentoalveolar posterior se midio linealmente y se analizo estadisticamente su variacion entre las maloclusiones, asi como la correlacion multiple entre las alturas dentoalveolares y APDI en T1 y T2. Resultados: el analisis intragrupo, evidencio el aumento significativo entre la dimension vertical dentoalveolar post rior en clases I y II con extracciones en T1 y T2, a nivel del segundo premolar inferior (5i) y segundo molar superior (7s), respectivamente. El analisis intergrupo, mostro aumento significativo al comparar la dimension vertical dentoalveolar posterior, segun la clasificacion esqueletica en tratamientos con extracciones a nivel del segundo premolar (5s), primer molar (6s) y segundo molar (7s) superiores y primer molar (6i) inferior. Conclusiones: se encontro aumento en la dimension vertical dentoalveolar posterior en todos los grupos en T1 y T2, siendo significativo en los grupos clases I y II con exodoncias de primeros bicuspides pero sin evidenciar cambios en la clasificacion esqueletica (APDI). ABSTRACT. Introduction: the purpose of this study was to determine and to cephalometrically compare the variation of posterior dentoalveolar vertical dimension in orthodontic patients treated with and without extraction of first premolars in Class I and Class II malocclusions and to establish its correlation by means of the Anteroposterior Dysplasia Indicator (APDI). Mehods: pre (T1) and post (T2) treatment lateral cephalograms of 76 patients from Fundacion CIEO, aged 22 to 45 years, were skeletally classified according to APDI and the type of treatment received, regardless of gender, forming four groups: Class I with and without extractions, and Class II with and without extractions. The posterior dentoalveolar vertical dimension was calculated with linear measurements and its variation among the malocclusion groups was statistically analyzed; also, a multiple correlation analysis between dentoalveolar heights and APDI was performed at T1 and T2. Results: the intragroup analysis showed a significant increase of posterior dentoalveolar vertical dimension at T1 and T2 in both Class I and Class II groups with first premolar extractions at the lower second premolar (5i) and upper second molar (7s), respectively. The intergroup analysis showed a significant increase in posterior dentoalveolar vertical dimension, according to skeletal malocclusion class, in treatments with first premolar extractions, at the upper second premolar (5s), upper first molar (6s), upper second molar (7s), and lower first molar (6i). Conclusions: there was an increase of posterior dentoalveolar vertical dimension at T1 and T2 in all the groups, being statistically significant in Class I and Class II patients treated with first premolar extractions without altering the skeletal classification (APDI).