VectorP ×VectorQ -It is the cross product of the vectors p and q and it will lie in a plane perpendicular to that of P and Q.Its direction could be determined by right hand thumb rule..
VectorQ×VectorP -Same like mentioned above.This will lie in plane perpendicular to the vectors P and Q but opposite to Vector P ×Vector Q .
Thus.. since VectorP×VectorQ and VectorQ×VectorP are opposite in direction,So the angle between them would be 180 degrees.