1. Introduction

2. Observations and data reduction
2.1. 480–1850 GHz Herschel/HIFI data
2.2. 330–373 GHz JCMT data

3. The HIFI spectral survey of AFGL 2591

4. Discussion
4.1. CI and CII
4.2. CO and its isotopologues
4.3. HCO+
4.4. N-bearing species
4.5. S-bearing species
4.8. HF
4.9. HCl
4.10. Complex species

5. Conclusions