We propose a simple structure for manipulating resonant conditions in random structures, which is composed of a waveguide structure as a defect region embedded in a random structure. Using the two-dimensional finite-difference time-domain method, we examine the resonant properties of localized modes bound in the waveguide. From the results, we confirm that long-lived modes are strongly confined in the waveguide only when the resonant frequency matches the frequency windows in the transmitted intensity spectrum of the surrounding random structure. (C) 2009 Optical Society of America