Same genus, different species. BTW, all of the poison ivy on my place climbs trees, which apparently makes it eastern poison ivy, per this page from the CDC:Poison oak, is a vine that climbs trees, Poison Ivy is a stand alone plant. Same basic plant, but cousins.
http://www.cdc.gov/niosh/topics/plants/
That page also indicates that we get both eastern (normally a vine) and western (normally a shrub) poison ivy, but only Atlantic poison oak. Lucky us.