REASONS FOR PERFORMING STUDY: To investigate laryngeal function in cases of recurrent laryngeal neuropathy pre‐ and post laryngoplasty (LP) using dynamic respiratory endoscopy (DRE). OBJECTIVES: To compare the rima glottidis area during DRE pre‐ and post LP; document all forms of dynamic upper airway obstruction (DUAO) pre‐ and post LP and investigate the relationship between post operative abduction at rest and exercise. STUDY DESIGN: Prospective case series. METHODS: Thoroughbred racehorses with pre‐ and post LP DRE were included. Left‐to‐right arytenoid cartilage angle ratios and rima glottidis area ratios were used to quantify laryngeal function during rest and exercise, pre‐ and post LP. RESULTS: In 35 horses, mean pre‐LP ratios were greater during rest (left‐to‐right quotient angle ratio LRQ 0.76 ± 0.13; left‐to‐right arytenoid ratio LRR 0.72 ± 0.14; rima glottidis area ratio RGA 0.40 ± 0.10) than exercise (LRQ 0.39 ± 0.16, P<0.001; LRR 0.38 ± 0.16, P<0.001; RGA 0.15 ± 0.05, P<0.001). Exercising ratios were larger post LP (LRQ 0.61 ± 0.13; LRR 0.60 ± 0.12; RGA 0.30 ± 0.08) than pre‐LP (LRQ 0.39 ± 0.16, P<0.001; LRR 0.38 ± 0.16, P<0.001; RGA 0.15 ± 0.05, P<0.001). A positive linear relationship was found between post LP resting and exercising ratios (R² = 0.48; P<0.001) and post operative abduction grades (R² = 0.63; P<0.001). Pre‐LP all horses demonstrated left arytenoid cartilage collapse with bilateral vocal cord collapse and 37% had aryepiglottic fold collapse. Post LP 13 horses (37%) developed additional DUAOs and these horses had smaller RGAs (0.25 ± 0.08) than horses that did not develop DUAOs (0.32 ± 0.07, P = 0.01). CONCLUSIONS: Multiple forms of DUAO occurred pre‐LP and additional forms often developed post LP. Post LP the degree of arytenoid cartilage abduction at rest was useful to predict the degree of abduction during exercise.