Frequency-dependent electrical characteristics of Ag/p-InP diodes have been determined using impedance spectroscopy at room temperature. Series resistance (R,) and interface state(s) (N-ss) values were extracted from capacitance (C) and conductance (G/w) data using the Nicollian and Goetzberger and Hill-Coleman methods, respectively. C and G/w data were also corrected in the whole measured bias voltage range to obtain real diode capacitance C-c and conductance G(c) values in order to see the effects of R-s. Both the C-V and R-s-V plots showed anomalous peak in depletion region especially at low frequencies due to the existence of N-ss. C-V and G/w-V plots crossed at a certain bias voltage and this point shifted toward negative bias voltages with increasing frequency and then disappeared at 3 MHz. Also, decrease in C values corresponds to an increase in G/w values in the same bias voltages. (C) 2012 Elsevier Ltd. All rights reserved.