(1) Background: Computed tomography (CT) is considered mandatory for assessing the
extent of pathologies in the paranasal sinuses (PNS) in chronic rhinosinusitis (CRS). However, there
are few evidence-based data on the value of ultrasound (US) in CRS. This multicenter approach
aimed to compare diagnostic imaging modalities in relation to findings during surgery. (2) Methods: 127 patients with CRS were included in this prospective multicenter study. Patients received
preoperative US and CT scans. The sensitivity and specificity of CT and US were extrapolated from
intraoperative data. (3) Results: CT scans showed the highest sensitivity (97%) and specificity (67%) in
assessing CRS. Sensitivities of B-scan US were significantly lower regarding the maxillary sinus (88%),
the ethmoid sinus (53%), and the frontal sinus (45%). The highest overall sensitivity was observed
for assessing the pathology of the maxillary sinus. (4) Conclusions: We observed high accuracy
with CT, confirming its importance in preoperative imaging in CRS. Despite the high US expertise
of all investigators and a standardized examination protocol, the validity of CT was significantly
higher than US. Ultrasound of the PNS sinuses is applicable in everyday clinical practice but lacks
diagnostic accuracy. Nevertheless, it might serve as a complementary hands-on screening tool to
directly correlate the clinical findings in patients with PNS disease
