The invention, and subsequent development of external cavity quantum cascade lasers (EC-QCLs) has allowed relatively simple access to a wide spectral region for high resolution laser spectroscopy. In this Letter, we demonstrate the application of a broadly tunable 5.3 mu m EC-QCL to absorption spectroscopy on the fundamental band of deuterium bromide. The large tuning range is utilised to record spectra allowing the hyperfine coupling constants to be determined for the v = 0 and v = 1 levels of both (DBr)-Br-79 and (DBr)-Br-81. We present the first measurement to our knowledge of e(2)Qq(v = 1) for (DBr)-Br-81, given a value of 460.5 +/- 12 MHz. (C) 2010 Elsevier B. V. All rights reserved.