Femoral shaft fracture in child is a disabling injury. Different methods of treatment can be used for femoral shaft fracture and depends on patient condition.The aim of the study was to evaluate lower limb discrepancy following different method of treatment and possible related factors especially type of fractures.Material and methods. This retrospective cross sectional study was carried out in Imam Khomeini and Razi Hospital from 2003-2007 on children admitted to hospital with femur fracture. All children aged <12 years of age with diagnosis of femoral shaft fracture were included in this study. Different methods of treatment were flexible intramedullary nailing, rigid intramedullary nailing with Steinmann pin and spica casting, spica casting and closed reduction, and ORIF with plate and screw. Distance from hip to knee for each patient was determined in scanograms. Sex, age, side of involvement, type of fracture were recorded for each case. Analysis was done with SPSS ver. 16.0. ANOVAs, Chi-Square, and t-Test were used with CI=95%.Results. In this study, 253 cases (M=182, F=71) were included. One hundred forty-six (57.7%) cases had right involvement and 107 (42.3%) of cases had left side involvement. From all cases, 135(53.4%) cases had no changes in lower limb length. Eleven (4.3%) cases had lower limb shortening and 107(42.3%) cases had lower limb lengthening. Type A1 and type A2 showed greatest lower limb discrepency among cases who underwent ORIF with screw & plate fixation, and spica casting with closed reduction respectively (p<0.05).Conclusions. There is significant difference among surgical and non surgical treatment for LLD. Spica casting and closed reduction has the least changes compared to other methods. Sex, side of involvement, type of fracture, and location had no effect in post operative length changes. Type of fracture, only, has a role in screw and plate fixation group and this is may be due to the differences between A1 and A3 fractures. Most of the changes were seen in the range of 60 through 120 months of age. Most of the changes were in the range +10 to +20 mm.