BACKGROUND Respiratory therapy is an integral part of treatment of cardiac patients. The aim of this study was to evaluate the effect of addition of inspiratory muscle training (IMT) to second-stage cardiac rehabilitation on exercise tolerance and function of lower extremities in patients following myocardial infarction (MI). MATERIAL AND METHODS This study included 90 patients (mean age 65 years) with MI who took part in the second stage of an 8-week cycle of cardiac rehabilitation (CR). They were divided into 3 groups: group I underwent CR and IMT, group II only underwent CR, and group III only underwent IMT. Groups I and II were allocated randomly according sealed opaque envelopes. The third group consisted of patients who could not participate in standard rehabilitation for various reasons. Before and after the 8-week program, participants were assessed for maximal inspiratory and expiratory pressure (PImax and PEmax) values, exercise tolerance, and knee muscle strength. RESULTS In groups I and II, a significant increase in the PImax parameters and exercise tolerance parameters (MET) were observed. Group I had increased PEmax parameters. In group III, the same changes in the parameter values that reflect respiratory muscle function were observed. All of the examined strength parameters of the knee joint muscles demonstrated improvement in all of the investigated groups, but the biggest differences were observed in group I. CONCLUSIONS Use of IMT in the ambulatory rehabilitation program of MI patients resulted in improved rehabilitation efficacy, leading to a significant improvement in physical condition.