Duda, during a joint press conference with Alar Karis in Tallinn, said on Friday that today both countries have completely different possibilities than when World War II began.
"Today we can organise help. We can also discuss sanctions with our allies and colleagues. We can use various modern solutions that are painful for Russia, which will show Russia that it does not and will not rule the world, our world," he said.
"President (Karis- PAP) and I are both looking at Ukraine... very closely - not only at Kyiv, but also at Irpin and Bucha... and we have no doubt that we must help Ukrainians to defend themselves... we try to act wherever possible," Duda said.
Karis said that he and Duda had talked about further support for Ukraine, which "must be our daily concern" and also discussed "how to make sure that the price of this invasion will be even greater for Russia."
He said that "the suffering of Ukrainians and Ukraine weighs on President (Vladimir) Putin, who must pay for it."
The Estonian president noted that whereas by its aggression against Ukraine Russia's intention was to weaken the European Union and Nato, "it achieved the opposite" and the EU and Nato "are more united and stronger than ever before."
"The war started by the Kremlin in the heart of Europe brings Finland and probably also Sweden to Nato, it also means that the Baltic Sea will be Nato's internal sea, which makes our security even stronger," Karis added.
According to Duda, the two presidents also talked about building alternative sources of energy for Poland, Estonia and neighbouring countries.
"We talked about this also because we hope for Nato's enlargement with neighbours from Finland and - we hope - also from Sweden, in the short term," Duda said.(PAP)