The aim of this research was to study the relationship between habituated posture when resting and postural deformities of upper trunk. The statistical population of this study consisted of all female students in dormitories of Shiraz state universities (Shiraz University, Industrial University and University of Medical Sciences) (N = 4500 people). 402 students were selected randomly. A researcher-made questionnaire was used to study the way of resting and spinal column conditions (validity 83%). It was distributed among students and then their body postures were studied by New York test, checkered sheet and plumb line. To measure the angles of thoracic and lumbar curve, the flexible ruler was used. Its validity was reported as 78% when compared to radiography technique. The data were analyzed by statistical software SPSS.10 and Spearman test (??0.05). The results showed no significant relationship between sleeping on back with stretched legs and lumbar lordosis and also between sleeping on back and raising hands with scoliosis and uneven shoulder. Also there was no significant relationship between side sleeping and bending legs and head into stomach to kyphosis and between side sleeping and the upper knee on the ground (with turning pelvis) to scoliosis. In this research, a significant relationship (r=0.39, P=0.037) was found between side sleeping while upper trunk was located farther than lower extremities and lumbar lordosis; also between sleeping on stomach and lumbar lordosis. The results showed no significant relationship between sleeping on stomach and neck lordosis, but there was a significant relationship between sleeping on stomach and kyphosis. The findings of this research did not show any significant relationship between the weight of the subjects and the sleeping condition and spinal column disorders; however, there was a significant relationship between the height of the subjects and side sleeping and upper knee on the ground. According to the results, there was a significant relationship between some resting conditions and postural deformities of upper trunk. It seemed that the effect of resting condition on deformities of upper trunk was not serious but it is necessary to make the students aware and to correct incorrect resting habits.