Background: Independently of the patient, the aerodynamic performance of a dry powder for inhalation depends on the formulation and the dry powder inhaler (DPI). In the case of capsule-based DPIs, the capsule also plays a role, not only in the packaging of the formulation, but also in the powder aerosolisation and the dispersion of the micronised drug from the carrier during inhalation. Therefore, the capsule is an important parameter. However, few studies have been conducted on the impact of the kind of capsule on aerodynamic performance. Methods: This study evaluated the impact of different capsules (Quali-GTM and Quali-V®-I from Qualicaps®, and hard gelatin capsules for DPIs, Vcaps® and Vcaps®Plus from Capsugel®) on the delivered doses (DDs) and fine particle doses (FPDs) of formoterol-based binary and ternary blends using the Axahaler® DPI. Results: Similar trends were observed for the DD, FPD and formoterol capsule retention for both dry powder formulations contained in the different capsules. The highest DDs and FPDs and the lowest formoterol capsule retention were observed with hypromellose capsules such as Quali-V-I and Vcaps, without significant differences between these capsules (p ˃ 0.05, one-way ANOVA with Newman-Keuls post-hoc test) for both dry powders. The ternary blend showed higher and less sensitive FPDs to the kind of capsules used than those observed for the binary blend. Conclusion: The choice of the kind of capsule used to package the dry powder has an influence on its aerodynamic performance, with the best results obtained from hypromellose capsules (Quali-V®-I and Vcaps®) for the binary and ternary mixtures used in this study.