Aim: To analyse the effectiveness and reliability of <K-angle cephalometric index usage in mixed dentition and to assess the correlation between differen types of facial skeleton growth patterns. Materials and Methods: 52 high-quality cephalograms were randomly selected from the archives of the Bogomolets National Medical University Dental Medical Centre and divided into three groups according to facial skeleton growth patterns and into subgroups according to Engle’s malocclusion classes. Multifactorial analysis of variance (ANOVA) was used to identify statistical differences between the mean angular values of studied groups; a p-value . 0.05 was considered statistically significant. Pearson’s correlation coefficient was used to assess the correlation between angles. Results: According to our study results, statistically significant correlation was found among patients in the first group between ANB and K angles and neutral growth type (p=0.005); significant correlation was found between the K and APDI angles and horizontal growth pattern (p=0.002); statistically significan correlation was found between the APDI parameter and both angles with vertical growth (p=0.001). According to the results of multifactorial ANOVA analysis of the mean values of the studied angles, there were no statistically significant differences in the <K, <ANB, and APDI parameters between all groups at the level of p . 0.05. Conclusions: The K-angle revealed to be the most valid and reliable indicator of sagittal jaw discrepancy assessment among all cephalometric parameters. <K index can be a full-fledged alternative to ANB angle during mixed dentition.