Spectral features of quantum systems can be extracted from dynamical quantities like wavefunctions or correlation functions. Using a time-dependent framework, we study symmetric transition state resonances of the collinear H + H-2 system, We compare time-dependent semiclassical results and the corresponding spectra to full quantum calculations. The semiclassical time-domain approach, which includes phase information and therefore allows for interference effects, reproduces the quantum results to a high degree of accuracy. Particularly, it has been possible for the first time to determine resonance widths for a generic molecular system semiclassically.