Ground state properties of the two-dimensional 3He–4He mixture are studied at zero temperature. We find that at low concentrations 3He atoms dimerize and form bosonic mixture with 4He. The binding energy of the dimer ranges from 10−3 K near the saturation density to 10−6 K at the solidification density. The radius of such a weakly bound dimer is tens of Ångströms. A stable atomic mixture is found at concentration larger than ≈5% varying with density. At high 3He concentrations the mixture phase separates and critical concentrations are obtained by calculating the second derivative of the enthalpy.