Background: Nasal nitric oxide (nNO) is an established screening tool for primary ciliary dyskinesia (PCD). Customary chemoluminescence-based analyzers preclude large-scale screening for PCD. Portable devices with electrochemical sensors have not been clinically validated. Objective: To compare test success and nNO levels between a chemoluminescence analyzer (CLD88 sp ^®) and a portable device (NIOX MINO ^®) in clinical routine, and to assess whether a tidal breathing velum-closure (TBVC) technique increases test success. Methods: Measurements were performed in children ≥3 years using a conventional single-breath maneuver against an expiratory resistance (ER) for CLD88, and a breath-hold (BH) technique for NIOX. TBVC was evaluated for both devices. Results: 120 children referred for investigation of respiratory symptoms were included (median age 9.9 yrs, range 3.1–18.5). For conventional breathing techniques, test success increased from preschool age (CLD88 10% and NIOX 3.3%) to adolescence (87.5% and 65%). TBVC increased test success for both devices (preschoolers 80% and 70% vs adolescents 97.5% and 97.5%; p<0.001 for all age groups). Median nNO was higher for CLD88 with 263.3 nL/min (ER) and 283.7 nL/min (TBVC) compared to NIOX with 214.5 nL/min (BH) and 208.1 nL/min (TBVC) (p=0.013 and p<0.001). Conclusion: Test success is low when conventional breathing techniques are applied, especially in younger ages, but can be increased by TBVC. Nasal NO levels are lower for electrochemical sensor devices compared to chemoluminescence analyzers with no difference between conventional and TBVC methods, without clinical relevance. These findings support using portable analyzers with TBVC as a promising screening tool for PCD.