Oliviero Diliberto, secretary of the Party of Italian Communists, said in his message the CPC congress was convened at a critical juncture concerning world balance and China's rise was changing the international pattern.
China's achievements in economic development had attracted world attention and its drive in poverty reduction had proved to be very fruitful, the message said.
The Party of Italian Communists was willing to advance its friendly and cooperative relations with the CPC in a concerted effort to attain the ideal of a socialist society, it said.
In a congratulatory note, Paolo Ferrero, secretary of Italy's Communist Refoundation Party said his party enjoyed brotherly relations with the CPC and was willing to strengthen bilateral cooperation to build a just and peaceful world.
Tom Curran, general secretary of Ireland's Fine Gael, said in a message his party viewed with great interest on-going economic, social and cultural development in China and looked forward to stengthening relations between the two countries.
He voiced hope the deliberations of the congress ensured the great progress being made was continued and enhanced.
Bohuslav Sobotka, leader of the Czech Social Democratic Party, said in his note the CPC congress was an important meeting in the CPC's history, which served as a link between past and future.
Following the guidelines of reform and opening up, China would continue to develop and benefit all its people, the message said.
The traditional friendly ties between the two parties would also be further cemented to promote the development of relations between the two nations and create a more just, harmonious and united world, it said.
Vladimir Voronin, president of Moldova's Party of Communists, said in his congratulatory message that, against the backdrop of the world economic crisis, the CPC had achieved success in building a modernized socialist country and effectively coped with the grave challenges posed by a multi-polarized world.
Cooperation between the two political parties was of strategic significance, the message said.
The political council of the New Azerbaijan Party said the political resolutions the 18th CPC congress made would ensure China's continuous, comprehensive and rapid growth, and would have a significant impact on promoting China's prestige in the region and the world.
The New Azerbaijan Party considered party-to-party dialogue a key factor for further deepening coordination between Azerbaijan and China and maintaining the interests of the two peoples.
The party was ready to further efforts to promote cooperation between the two parties, it said in a message.
Petr Simonenko, first secretary of the Ukrainian Communist Party, believed the CPC would stick to the successful path of China's development as always, lead the Chinese people to new victory and achievements, and realize the magnificent blueprint of the country's development.
Jorge Moreira da Silva, first vice president of the Social Democratic Party of Portugal, said China, as a driving force of world peace, development and prosperity, was playing an unprecedentedly important role and winning global recognition.
The decisions the 18th CPC congress made would benefit the Chinese people and society, he said.
The Christian Democratic Union of Germany said in a congratulatory message China held important functions in Asia as well as the world.
"In the 21st century, we all face various challenges. Not a single country can deal with them separately. But fortunately, we can talk about ways to tackle these problems with China," the party said.
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