This article concerns preferential orientations of the crystal a-axis for the standard type PBO AS and high modulus type HM fibers. The degree of radial preferential orientation of the crystal a-axis along the fiber radius direction was analyzed based on a newly-proposed 3D two-phase model. The result was compared with the previously analyzed three PBO fibers made through water vapor, hot water and nonaqueous coagulation processes. The proposed model fitted well the measured micro-focus X-ray scattering patterns of the (200) crystal plane as a function of the position of the fiber on which the source beam was focused. The crystal orientation of the c-axis was strictly estimated from the three equatorial diffractions based on Wilchinsky's generalized model. (C) 2015 Elsevier Ltd. All rights reserved.