Although a concrete-filled steel tube (CFT) column, which is one of the composite columns frequently used in building construction because of its structural performance, economic feasibility, and good space utilization, has a high potential to reduce CO2 emissions because of combining two heterogeneous materials, the relationship among CO2 emissions, cost, and structural parameters in green construction of buildings with CFT columns was not yet carried out. In this study, an optimum design model was proposed to analyze the relationship. Based on the analysis, it was founded that CFT with circular sections were more effective than square type in terms of CO2 emissions and cost by 57.03% and 11.18%, respectively, while square type was advantageous in aspect of space utilization than the circular section by 9.73%. Also, with the consideration of various strengths of materials, CO2 emissions, cost, and space utilization for the columns can be reduced by 24.38%, 29.66%, and 21.08%, respectively. In addition, the proposed model was applied to construction of a 35-story real building. From the analysis of optimum designs for the building, the circular section was more advantageous than square section regarding the CO2 emission and material cost by 2.47% and 8.57%, respectively, while square section occupied smaller space than circular section by 17.95%. It is concluded that CO2 emission, cost, and space utilization of the column in the real building can be reduced by 21.05%, 14.97%, and 20.18%, respectively, with the optimum section type and material strength. (C) 2016 Elsevier B.V. All rights reserved.