Scaffolds with multimodal pore structure are essential to cells differentiation and proliferation in bone tissue engineering. Bi-/multi-modal porous PLGA/hydroxyapatite composite scaffolds were prepared by supercritical CO2 foaming in which hydroxyapatite acted as heterogeneous nucleation agent. Bimodal porous scaffolds were prepared under certain conditions, i.e. hydroxyapatite addition of 5%, depressurization rate of 0.3 MPa.min(-1), soaking temperature of 55 degrees C, and pressure of 9 MPa. And scaffolds presented specific structure of small pores (122 mu m +/- 66 mu m) in the cellular walls of large pores (552 mu m +/- 127 mu m). Furthermore, multimodal porous PLGA scaffolds with micro-pores (37 mu m +/- 11 mu m) were obtained at low soaking pressure of 7.5 MPa. The interconnected porosity of scaffolds ranged from (52.53 +/- 2.69)% to (83.08 +/- 2.42)% by adjusting depressurization rate, while compression modulus satisfied the requirement of bone tissue engineering. Solvent-free CO2 foaming method is promising to fabricate bi-/multi-modal porous scaffolds in one step, and bioactive particles for osteogenesis could serve as nucleation agents. (C) 2017 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.