Metal-semiconducting diamond (MS) and metal-insulating diamond-semiconducting diamond (MIS) contacts were fabricated on the same type IIb single crystal diamond. Direct comparisons of MS and MIS structure characteristics were made by analysis of current-voltage and differential capacitance-voltage (C-V) data. Both the MS and MIS contacts exhibited good rectifying characteristics, with a 5 V rectification ratio > 10(6). The depletion layer uncompensated acceptor concentration measured in both structures by C-V analysis was -1.8 X 10(16) cm-3.