During the '40s and '50s during Stalin's reign, the two were very similar, as Stalin exerted great influence upon China and Mao Zedong's policy, however after Stalin's death and the market reforms in the Soviet Union, they started to become distant due to Mao Zedong's more hardline policies (leading to the Sino-Soviet split), and after Mao's death In the late '70s with Deng Xiaoping succeeding him and also making more market reforms and converting China to less hardline policies, they started to become alike again until the early '90s when the Soviet Union collapsed and turned into a federal republic, again becoming more distant.
TL;DR
They were close under Stalin and Mao, but distant after Stalin's death, but alike with Deng and his successors and Stalin's successors.
