Objective:To assess thoracoabdominal asynchrony (TAA) and inspiratory para-doxical motion at different positionings in subjects with Duchenne muscular dys-trophy (DMD) versus healthy subjects during quiet spontaneous breathing (QB) andcough.Methods:This is a case control study with a matched‐pair design. We assessed 14DMD subjects and 12 controls using optoelectronic plethysmography (OEP) duringQB and spontaneous cough in 3 positions: supine, supine with headrest raised at45°, and sitting with back support at 80°. The TAA was assessed using phase angle(θ) between upper (RCp) and lower rib cage (RCa) and abdomen (AB), as well as thepercentage of inspiratory time the RCp (IPRCp), RCa (IPRCa), and AB (IPAB) moved inopposite directions.Results:During cough, DMD group showed higher RCp and RCaθ(p< .05), RCp andABθ(p< .05) in supine and 45° positions, and higher RCp and Rcaθ(p= .006) only insupine position compared with controls. Regarding the intragroup analysis, duringcough, DMD group presented higher RCp and ABθ(p= .02) and RCa and ABθ(p= .002) in supine and higher RCa and ABθ(p= .002) in 45° position when com-pared to 80°. Receiver operating characteristic curve analyzes were able to dis-criminate TAA between controls and DMD in RCa supine position (area under thecurve: 0.81, sensibility: 78.6% and specificity: 91.7%,p= .001).Conclusion:Subjects with DMD yields TAA with insufficient deflation of chest wallcompartments and rib cage distortion during cough, by noninvasive assessment.