This paper reports an analytical and numerical study of double-diffusive natural convection through a fluid-saturated, vertical and homogeneous porous annulus subjected to uniform fluxes of heat and mass from the side. The influence of each leading parameter and especially curvature, a major parameter of this geometry, has been numerically investigated. Solutions are presented for 1 less than or equal to A less than or equal to 10, 1 less than or equal to Ra-T less than or equal to 200, 1 less than or equal to Le less than or equal to 20, 0.1 less than or equal to N less than or equal to 10 and 0 less than or equal to gamma less than or equal to 10 where A, Ra-T, Le, N and gamma denote the aspect ratio, thermal Rayleigh number, Lewis number, buoyancy ratio and curvature parameter, respectively. For the steady state, an analytical solution valid for stratified flow in slender enclosures is presented. A good agreement is observed between the analytical predictions and the numerical simulation for sufficiently high aspect ratios.