Spectral retrieval has proven in the past several years to be a powerful tool for constraining the physical properties of exoplanet atmospheres as well as measuring their chemical compositions. Obtaining high signal-to-noise and hence information-rich spectra of exoplanets is observationally challenging, especially for directly imaged companions. Thus, spectral retrieval for such objects has been performed only for only several objects. I will discuss some of the difficulties that need to be overcome to make atmospheric retrieval of a substellar companions in detail routine. I will also discuss several scientific questions that can be answered using this technique.