Hierarchically organized gamma-AlOOH hollow spheres with nanoflake-like porous surface texture have been successfully synthesized via an ionic liquid-assisted hydrothermal synthesis method in citric acid monohydrate (CAMs). It was found that ionic liquid [bmim]Cl-+(-) played an important role in the morphology of the product due to its strong interactions with reaction particles. The samples were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscope (SEM) and Transmission Electron Microscopy (TEM). The results show that the product has narrow particle size distribution (500-900 nm particle diameter range), high specific surface area (240.5 m(2)/g) and large pore volume (0.61 cm(3)/g). The corresponding gamma-Al2O3 hollow spheres can be obtained by calcining it at 550 degrees C for 3 h. The proposed formation mechanism and other influencing factors of the gamma-AlOOH hollow sphere material, such as reaction temperature, reaction duration, CAMs and urea, have also been investigated. (C) 2012 Elsevier Ltd. All rights reserved.