<p>The diagnosis of pneumonia is based on implicative clinical signs and symptoms and the presence of a new infiltrate on chest X-ray. Point of care lung ultrasound may be an alternative as well as an adjunct diagnostic tool. However, infiltrations in chest X-ray have poor sensitivity and specificity resulting in a positive predictive value of only 60%-75% for community-acquired pneumonia (CAP) in hospitalized patients and bear high inter observer variability. The reasons are manyfold such as coincident pulmonary diseases, variability of infiltrations during the disease course of CAP and numerous differential diagnosis imposing similar infiltrations which are discussed in this paper. Although not recommended in the first line of diagnostic work-up, a CT-scan is the next logical step to clarify an ambiguous chest X-ray result. But also here, a significant overlap to other respiratory, infectious or non-infections conditions may confuse the correct diagnosis, implicating that pulmonary infiltrates in radiologic images are only one step in the diagnostic puzzle.</p>