A discrete-time filter for GSM/WCDMA/WLAN with area reduction technique is presented. The discrete-time filtering is suitable for pass band selection and anti-alias filtering. Reduction of large switched-capacitor area is a key issue for the filter. In this paper, we propose the retiming technique and the optimization of unit capacitor to reduce the number of capacitors. The area of the filter with IQ channels is 1.8 mm<sup>2</sup> . Noise Figure (NF) and current consumption in GSM mode are 23.2 dB and 11 mA, respectively. This filter is fabricated in 0.13 um CMOS.