The equilibrium properties of an aluminum impurity trapped in solid para-hydrogen have been studied. The results were compared to those of a previous study by Krumrine et al. [J. Chem. Phys. 113 (2000) 90791 with an atomic boron. In the presence of vacancy defect, when the orientation-dependent Al-pH(2) potential is used, the Al atom is displaced to a position half way between its original substituted site and the vacancy site. Thermodynamic results also indicate that the presence of a neighboring vacancy helps to stabilize the Al impurity to a far greater extent than in the case of the B impurity. (C) 2002 Elsevier Science B.V. All rights reserved.