Quantum chemical fully ab initio conformational calculations were performed for the weakly bound van der Waals CO ⃛H2 dimer in the framework of the supermolecule approach. The counterpoise‐corrected interaction energies, computed through fourth‐order MBPT using the basis sets described recently by Sadlej, were in excellent agreement with results obtained with larger basis sets constructed to give accurate values for the electric moments and polarizabilities of CO and H2. The relative stability of the configurations studied here was collinear structures > parallel structure > T‐shaped structures. The collinear and parallel structures represent the most stable group of configurations. The present calculations show that they have values of De between 5.89 and 10.66 meV. The T‐shaped structures represent relatively less stable configurations with values of De between 0.84 and 2.92 meV. © 1995 John Wiley & Sons, Inc. Copyright © 1995 John Wiley & Sons, Inc.