Justin, who split with Selena in November 2012, uploaded two pictures of Selena at the Vanity Fair Oscars After Party last night before making his comment.
The troubled Canadian singer told his followers: "Most elegant princess in the world."
Justin, 19, and 21-year-old Selena were in a relationship for two years and, at one stage, were a serious teen power couple.
But it wasn't to be and following their break up, Justin hit the headlines for his wild behaviour and repeated brushes with the law.
Most elegant princess in the world. http://t.co/KGGn1u45Z9— Justin Bieber (@justinbieber) March 3, 2014
In January, however, Selena and Justin were spotted riding Segways together in Los Angeles, sparking rumours that they were about to reunite.
Days later, Justin shared a new photograph of himself and Selena on Twitter. It later emerged that Selena had checked into rehab that week, though not for substance abuse.
In December, Justin said that he would "love Selena to this day" during a radio interview.
Are they back on? We'll just have to watch this space...
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