The pressure effect up to 30 GPa on the structural and electronic properties of crystalline anthracene and tetracene were studied within the framework of density functional theory with van der Waals interactions. Lattice parameters, bulk modulus and cohesive energy were calculated. The pressure dependence of interplanar angles, which describe the relative packing of molecules in the crystal, has been calculated. The calculated electronic band structures demonstrate the dependence of energy gap under pressure. Energy gap in crystalline anthracene monotonously decreases with increasing pressure. The tetracene energy gap decrease from 2.39 to similar to 0 eV at 26 GPa. Further increase of pressure subsequently increases energy gap. (C) 2017 Elsevier B.V. All rights reserved.