Introduction: craniofacial growth and development can be evaluated through lateral head radiographs, in order to provide a good diagnosis and an effective treatment plan. Objective: to identify the relationship between the length of the upper jaw and the facial biotype in individuals aged 18 to 45 years in the city of Cuenca, Ecuador, during the year 2019. Method: a quantitative, descriptive and relational study was carried out; the sample was of 160 lateral head radiographs obtained in a maxillofacial dental radiology center in the city of Cuenca. AutoCAD software was used for the cephalometric tracing. For statistical analysis, the Kruskal-Wallis test and Tukey's post hoc test were used with a reliability level of 95% (p<0.05). Spearman's Rho correlation coefficient was used to determine the relationship between maxillary length (mm) and skeletal measurement. Results: it was found that the length of the upper jaw according to facial biotype is shorter in the upper jaw and increases in the lower; the tall facial biotype presented the shortest maxillary length (52.18±4.20 mm) and the highest average was the medium-low (54.37±4.15 mm). In males, the highest average was observed in the low biotype (55.38±4.55 mm) and the lowest value was in the medium high biotype (53.10±3.23 mm); in females, the highest average was found in the medium-low facial biotype (53.84±4.01 mm) and the lowest average was in the high biotype (51.64±3.68 mm). Conclusions: as the facial biotype increases, the length of the maxillary decreases. There is no significant relationship between maxillary length and age, or between length and sex.