TheT-matrix approach, which describes the scattering of acoustic waves (or of other waves) from objects of arbitrary shape and geometry, is here «married» to the resonance scattering theory in order to obtain the (complex) resonance frequencies of an arbitrary shaped target. For the case of nearly impenetrable targets, we split the partial-wave scattering amplitudes into terms corresponding tointernal resonances, plus an apparently nonresonant background amplitude which, however, contains the broad resonances caused byexternal diffracted (or Franztype, creeping) waves, in addition to geometrically reflected and refracted (ray) contributions.