A numerical study has been conducted to investigate the steady axisymmetric mixed convection boundary layer flow past a thin vertical cylinder placed in a water-based copper (Cu) nanofluid. Using appropriate transformations, the system of partial differential equations is transformed into an ordinary differential system of two equations, which is solved numerically using bvp4c function from Matlab. Numerical results are obtained for the skin-friction coefficient and Nusselt number as well as for the velocity and temperature profiles for some values of the governing parameters, namely, the nanoparticle volume fraction parameter phi, mixed convection parameter lambda and the curvature parameter gamma with the Prandtl number Pr = 6.2 (water). The results indicate that dual solutions exist when the surface of the cylinder is cooled (opposing flow, lambda < 0). It is shown that for a regular fluid (phi = 0) a very good agreement exists between the present numerical results and those reported by Mahmood and Merkin [8]. (C) 2011 Elsevier Ltd. All rights reserved.