Russians have voiced concern over EU expansion
While many Eastern Europeans celebrate their countries' accession to the EU, the mood beyond the union's new eastern border is more subdued.
In Belarus, Ukraine and Russia there is a mixture of unease about the impact of the expanded EU and disappointment at missing out on the benefits of membership.
In the Belarusian capital Minsk, riot police on Saturday tried to prevent an opposition demonstration in favour of EU enlargement, confiscating EU flags and arresting protesters.
The country's president, Aleksandr Lukashenko, has had less than cordial relations with Brussels, which has frequently criticised his human rights record.
In Russia, reaction to EU expansion reflects both concern over its new powerful neighbour and a desire to remain aloof.
The daily Nezavisimaya Gazeta believes staying out of the European Union may be the best thing for Russia, which it thinks has chances of becoming a new "European tiger" on its own.
The paper adds that an improving economy could give Russia bargaining power in relation to the EU, but warns that it should avoid frightening "old lady Europe" again in future.
It also urges Moscow to put pressure on the EU to prevent what it calls "discrimination" against the Russian-speaking minority in Latvia.
Many of the country's ethnic Russians do not have Latvian citizenship, and there have been complaints that the EU has done too little to encourage its new member to improve the minority's position.
In Latvia itself, Russian speakers on Saturday staged a protest against plans to end the teaching of Russian in schools across the street from a ceremony in Riga to mark the country's accession to the EU.
Between 20,000 and 30,000 protesters carried EU flags tied with black ribbons as a sign of mourning, according to agency reports.
Moscow's Vremya Novostei is dismissive of the benefits of EU membership, wondering whether the new members really know what they have let themselves in for.
"There is a strange European standard concerning the 'curvature' of bananas permitted for sale in the EU," it says, adding helpfully: "This is not a joke."
Another Russian paper, Rossiyskaya Gazeta points out that Russia's "long-suffering" enclave of Kaliningrad is now cut off from the mother country by the European Union.
"Hurrah, Russia will finally have a border with Europe! But what sort of hurrah is it if it wasn't us that came to Europe, but Europe that came to us," it says.
In neighbouring Ukraine, the mood is different, with many papers feeling left out of the European party.
"Our homeland has found itself on the sidelines of Europe, or to be more exact, in some other kind of Europe - an unpredictable and obscure one, one with a dubious future," the opposition daily Ukrayina Moloda notes ruefully.
The Ukrainian parliament's newspaper, Holos Ukrayiny, talks of an "enlargement of the EU which we no longer seek to enter", and says the government appears to have dropped ambitions to join the union.
"It has become obvious that, through no fault of ours, the prospect of seeing that strategy fulfilled appears doubtful," it says.
Fears of the economic repercussions of EU enlargement also exercise some papers, with tabloid Segodnya worried that Ukraine's vital industrial sector will lose access to previously open markets.
"Losses may amount to an average of 250m euros a year," it says.
Zerkalo Nedeli urges the EU not to "erect a high wall" on the Ukrainian border, but "help its neighbour become richer" instead.
In Lviv, close to the Polish border, the daily Vysokyy Zamok bemoans the fact that Ukraine has lagged behind its western neighbour, which has now become an EU member.
"Fifteen years ago the level of prosperity or, to be more precise, poverty in both Poland and Ukraine was identical, but now the gap is obvious," it says, and warns that the gap will widen unless Ukraine tries to benefit from EU expansion
"Ukraine should welcome the process of EU enlargement as a positive one and one which is beneficial for its future."
BBC Monitoring, based in Caversham in southern England, selects and translates information from radio, television, press, news agencies and the Internet from 150 countries in more than 70 languages.