The North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) are known as phenomena influencing the weather and climate of the Euro-Atlantic region. Often, however, they are treated together. In this study, two indices representing two independent teleconnection patterns in the sea level pressure are introduced to characterize their differences. One is a seesaw between the Azores and Iceland (AI), and the other is that between the Polar and Mediterranean (PM) regions. The result of our study shows that differences in the NAO/AO indices mainly arise from the inclusion of different portions of the AI and PM, and the NAO/AO indices can be reproduced by a linear combination of the AI and PM indices.