We compare observations of the binary system CM Draconis with synthetic spectra. Spectroscopic observations from 0.40 to 2.41μm, combined with photometry and the accurately known surface gravity enable us to estimate the temperature and metallicity using detailed spectra synthesis. We find discrepancies between the analysis of the infrared and optical spectrum: while the optical spectral energy distribution (SED) yields a metal-rich solution with Teff = 3000K, the infrared SED yields around 3200K and —0.8 ≤ [M/H] ≤ —0.6 compatible with the high space motion of the system. The low-metallicity characteristics of the infrared SED could be real and is partly supported by the detailed analysis of the atomic lines in the optical region. Although, the known incompleteness of the TiO and H2O line lists in the models may cause substantial systematic errors.