Chronic rhinosinusitis (CRS) can be associated with asthma, with a reported frequency of asthma in patients with CRS of up to 44%. COPD is another lung condition that can be associated with CRS. This longitudinal study reviewed the nasal and respiratory outcomes of 82 patients with CRS and concomitant asthma (45) or COPD (37) undergoing functional endoscopic sinus surgery (FESS). In asthmatic patients, spirometry indices (mean FEV1 and FVC) improved significantly following FESS, as did their ACT (Asthma Control Test) score. In patients with COPD, spirometry indices decreased very slightly in the six months after surgery, but CAT (COPD Assessment Test) scores improved significantly (from 15.70 to 32.11) after FESS (P < 0.001). The mean SNOT score in both groups was significantly reduced. Whilst it might be considered paradoxical for spirometry to worsen but symptoms to improve in patients with COPD, one explanation might be that the parameters assessed by the CAT are not particularly specific for COPD; for example, assessment of energy levels and quality of sleep. Mild spirometry worsening over six months would be consistent with the natural history of COPD. Another limitation of this study is the lack of blinding and absence of a suitable control group. In spite of the study’s limitations, this paper does ultimately provide further evidence for the beneficial effect of FESS with regards to improving asthma control from both a subjective and objective perspective. Patients with COPD and CRS are also likely to experience symptomatic benefit following FESS, but not necessarily because of improved COPD control.