This study aims to identify the most common postural deviations in 12 to 14-year old students in Muscat, the differences between postural deviations according to age category, the relation between the level of body mass index and such postural deviations and relation between postural deviations with each other. The study covers 852 students from basic grades of 7 to 9.The researcher used several tests and equipment including stature screen, Bancraft equipment, New York posture test, and foot print test.For analyzing the data, several statistical methods were used such as math average, standard deviation, percentage, number of repetitions, multiple difference analysis and Pearson Correlation Factor. The results of this study showed that the prevalence of postural deviations varies among the study sample. The most common deviations are the roundness of shoulders, flat feet, lumbar lordosis respectively. The level of postural deviations varied according to its prevalence among subjects from mild to clear deviations. There were also statistical differences between postural deviations of the subjects based on age category for lumbar lordosis in favour of the 12-year old students, while there was no statistical differences in the remaining deviations. The study also showed there is positive relationships between body mass index and lumbar lordosis, knock knees and flat feet.However, there is negative relationship between body mass index and round shoulders deviations. There is also positive relationship between some postural deviations and development of other compensatory such as the relationship between spine curving and lumbar lordosis, and between one should dropping and lateral bending. The researcher presented a number of recommendations such as the necessity to raise awareness of postural and health between students, periodical test of students' postural deviations through physical education classes.