In patients with stable coronary artery disease, the effect of oxygen (O2) inhalation to regional myocardial functions and its relation to the degree of the coronary artery stenosis is still unclear. This article investigates the effect of O2 therapy on regional myocardial functions in patients with coronary atherosclerosis according to the severity of stenosis. Myocardial segments were evaluated via tissue velocities, strain, strain rate, and tissue tracking. While O2 inhalation improves late diastolic myocardial velocity and tissue tracking in normally perfused myocardial regions, a negative effect was observed on systolic and diastolic parameters of myocardial segments, which are perfused by insignificantly stenotic coronary arteries. Although nasal O2 treatment has unfavorable effects on regional myocardial functions in patients with coronary artery disease, this effect remains subclinic with short-term inhalation. However, it is reasonable to pursue the effects of longer-term O2 inhalation on myocardial function especially in patients with insignificant coronary stenosis.