In this work, density functional theory calculations on the structural, mechanical, lattice dynamical, and thermodynamical properties of YB2 in AlB2-type and monoclinic (C2/m) structures are reported. The local density approximation has been used for modeling exchange-correlation effects. We have predicted the lattice constants, bulk modulus, elastic constants, shear modulus, Young's modulus, Poison's ratio, Debye temperature, and sound velocities. Furthermore, the phonon dispersion curves, corresponding phonon density of states, some thermodynamical quantities such as internal energy, entropy, heat capacity, and their temperature-dependent behaviors are presented. Our structural and some other results are in agreement with the available experimental and theoretical data. (C) 2010 Elsevier B.V. All rights reserved.