Functional endoscopic sinus surgery (FESS) is now a routine surgical procedure performed all around the world. A pre-operative computed tomography (CT) scan is considered mandatory in most countries where these are available but there are still some surgeons who question the need for imaging especially in patients due to undergo limited FESS or middle meatal antrostomy. There are excellent papers, describing how to read scans looking for anatomical abnormalities, but unfortunately their description of maxillary sinus hypoplasia and the associated uncinate process deformities are limited. This article describes two cases, one of unilateral and one of bilateral maxillary sinus hypopolasia (MSH) and discusses their implications. Awareness of these anatomical variants is crucial to avoid orbital complications.