Jiri Kuchar, who wrote two books on the collection, said Friday the paintings found at the Doksany monastery 50 kilometres (30 miles) north of Prague were worth about 50 million koruna (two million euros, $2.7 million).
"They're part of Hitler's collection of about 45 paintings, about 30 statues, a writing table and some gifts, which was declared former Czechoslovakia's war booty," Kuchar told AFP.
The paintings include the 1943 "Memory of Stalingrad" by Franz Eichhorst, who was "Hitler's ace painter," Kuchar said.
The collection was deposited at the southern Czech monastery of Vyssi Brod during World War II, together with two larger collections formerly owned by German-born Jewish banker Fritz Mannheimer and the Rothschild family.
After the war, the Americans took the Mannheimer collection bought by Hitler in 1941, and the Rothschild collection from Vienna confiscated in 1938, to Munich.
But they left behind the rest, which Kuchar says might be worth hundreds of millions of koruna at auction.
"The monks who got the monastery back after the war said they didn't want the paintings," said Kuchar, describing their journey through several castles and monasteries before ending up at Doksany, where he discovered them last July.
Kuchar began his research five years ago with pictures of the collection taken while it was still at Vyssi Brod.
"I sent DVDs with the pictures to institutions I thought might have the works," he said.
He managed to track down several statues and paintings, including a group of statues in the park of the southern chateau of Hluboka, which the administrator has since removed to prevent neo-Nazi tourism.
Kuchar also bemoaned the loss of some works in recent years: "To put it delicately, let's say they disappeared."
"I'm afraid there's a channel leading to the west. I've found two of the statues on offer at auction houses, one in Frankfurt, the other in London," he said, adding one was sold for 150,000 pounds (177,000 euros, $237,000) two years ago.