A novel I/Q (in-phase/quadrature) imbalance compensation scheme is proposed for quadrature-signal-mixing radio-frequency transceivers, employing either the direct-conversion architecture or the low-intermediate-frequency architecture. An adaptive DSP (digital signal processing) algorithm is developed for the proposed scheme, to on-line compensate the I/Q imbalance in both the transmitter and the receiver simultaneously, which is impossible for the other existing I/Q imbalance compensation schemes so far. In addition, the proposed scheme requires little extra calibration hardware, suffers no hidden errors introduced by the calibration circuitry, and is thus highly suitable for implementation in practical applications.