The pair won the Champions League with Real Madrid two years ago.
"I got on really well with Cristiano," Ancelotti told AS.
"He helped a lot in winning the Champions League, as everyone did. But now he's at Madrid and he's an adversary. Every squad has its characters. Madrid had Cristiano, Ramos, Kroos, Modric, Benzema…really strong players. Now I have another squad, and my work is the same. My goal is to have a good relationship with players, be it Cristiano or Lewandowski."