We examine the dissociative adsorption of hydrogen on metal surfaces by employing a reduced dimensionality quantum scattering method. Using hyperspherical coordinates, we show how the six-dimensional (6D) H-2/metal surface dissociation problem may be reduced to two dimensions by treating explicitly the bonds breaking and forming, while adding zero-point energy corrections to the effective potential for all other degrees of freedom. We present calculations of reaction probabilities for dissociation of H-2 on Ni(100) in three dimensions and on Cu(111) in four dimensions using this approach, and show their substantial agreement with those obtained using far more expensive exact methods. Five-dimensional and 6D results for H2Cu(111) are also presented, and compared to the lower-dimensional results.