Extrinsic causes of restrictive lung syndrome in idiopathic pulmonary fibrosis (IPF) patients have been poorly investigated. We aimed to investigate the influence of the anterior chest wall deformity, noninvasively assessed by modified Haller index (MHI), on spirometry parameters and outcome in a consecutive population of patients with mild-to-moderate IPF. 60 consecutive IPF patients (73.8 ± 6.6 yrs, 45 males) were included in this retrospective study. All patients underwent physical examination, spirometry, blood tests, conventional transthoracic echocardiography and MHI assessment (chest transverse diameter over the distance between sternum and spine) at basal evaluation. During follow-up, we evaluated the composite endpoint of 1) pulmonary or cardiovascular hospitalizations; 2) all-cause mortality. IPF patients with concave-shaped chest wall (MHI >2.5) (36.7% of total) and those with normal chest shape (MHI ≤2.5) (63.3%) were separetely analyzed. In comparison to IPF patients with MHI ≤2.5, those with MHI >2.5: were less likely to be men and smokers; had a more severe restrictive pattern; had significantly smaller cardiac chamber dimensions and significantly higher systolic pulmonary artery pressure (51.9±15.1 vs 42.4±14.3 mmHg, p=0.02). Mean follow-up time was 2.5±1.4 yrs. During follow-up, 13 deaths and 16 pulmonary or cardiovascular hospitalizations were detected. At multivariate Cox regression analysis, concave-shaped chest wall (MHI>2.5) (HR 4.55, 95%CI 1.02-20.4), increased C-reactive protein (HR 1.68, 95%CI 1.08-2.61) and absence of beta-blocker therapy (HR 0.13, 95%CI 0.01-0.26) were independently associated to the investigated outcome. MHI assessment and implementation may help the clinician to identify, among IPF patients, those with poorer prognosis over a medium-term follow-up.