BACKGROUND/OBJECTIVE: Office workers are exposed to high levels of sedentary time. This sedentary time may have impacts on office workers which affect the normal movement patterns of sitting position caused by muscle tightness and weakness. The aims of this study were to investigate postural changes in lower crossed syndrome (LCS) on a head tilt angle (HTA), craniovertebral angle (CVA), sagittal shoulder angle (SSA), and trunk flexion angle (TFA) during 30 min sitting in female office workers. METHODS: Fifty-four office workers who use computer for at least 4 h/day, work for at least 5 years were recruited. All subjects were evaluated their posture, muscle length and power and assigned into three groups: healty group ( ), LCS type A ( ), and LCS type B ( ). Testing posture was 30 min sitting at computer workstation and typing on standardized with video record. Then three pictures were captured at four points of time from VDO records. All angles were measured two-way mixed ANOVA and post-hoc Tukey test was used to analyse the data. RESULTS: Subjects with LCS type B have less CVA, SSA, and TFA than healthy and participants with LCS type A significantly during sitting at 0, 10, 20 and 30 min. There was no significant difference in HTA among the three groups. CONCLUSION: Subjects with LCS type B showed significant the upper body posture changes compared with other groups.