We review the use of both pulsed and continuous wave quantum cascade lasers in high-resolution spectroscopic studies of gas phase species. In particular, the application of pulsed systems for probing kinetic processes and the inherent rapid passage structure that accompanies observations of low-pressure samples using these rapidly chirped devices are highlighted. Broadband absorber spectroscopy and time-resolved concentration measurements of short-lived species, respectively exploiting the wide intrapulse tuning range and the pulse temporal resolution, are also mentioned. For comparison, we also present recent sub-Doppler Lamb-dip measurements on a low-pressure sample of NO, using a continuous wave external cavity quantum cascade laser system. Using this methodology the stability and resolution of this source is quantified. We find that the laser linewidth as measured via the Lamb-dip is ca. 2.7 MHz as the laser is tuned at comparably slow rates, but decreases to 1.3 MHz as the laser scan rate is increased such that the transition is observed at 30 kHz. Using this source, wavelength modulation spectroscopy of NO is presented.