The “Pacific Decadal Oscillation” (PDO) has been described by some as a long-lived El Nino-like pattern of Pacific climate variability. Although there are several mechanisms to explain such multi-year persistence of upper ocean temperature anomalies the origin to cause PDO variability remains unclear. According to previous studies PDO fluctuations during the 20th century were more energetic on decadal-to-interdecadal timescales. In this paper we examine changes in PDO under climate change projections using the AR4-IPCC coupled general circulation models (CGCMs). In particular, we focus on changes in PDO characteristics in relation to El Nino and Southern Oscillation (ENSO) by directly comparing the SRES A1B climate change projections with the 20C3M control experiment. Our preliminary results indicate that a linear relationship between PDO and ENSO is stronger in SRES A1B experiment than in the 20C3M experiment. Such change may be due to changes in ENSO properties or changes in tropics-midlatitudes teleconnections under global warming. In addition, it is found that there are some regional differences of PDO under global warming in terms of its spatial structure and intensity compared to the 20C3M experiment.