Moving from the anisotropic interpolation error estimates derived in Formaggia and Perotto, (2001), we provide here both a-priori and a-posteriori estimates for a generic elliptic problem. The a-priori result is deduced by following the standard finite element theory. For the a-posteriori estimate, the analysis extends to anisotropic meshes the theory presented in Becker and Rannacher, (1995, 1996, 1999). Numerical test-cases validate the derived results