* Both presidents hit it off over lunch in 2005
* Likely to see eye-to-eye on North Korea
* China annual trade with S.Korea worth $215 bln; $6 bln with North
* South Korean firms have invested $40 bln in China
* Chinese love South Korean fashion, pop stars and soap operas
By Ju-min Park
SEOUL, June 24 (Reuters) - When the presidents of China and South Korea meet in Beijing this week, they will likely use a rapport that blossomed eight years ago to find common ground on North Korea as well as seek ways to boost already vibrant economic ties.
With her self-taught Mandarin and interest in Chinese culture, South Korea's Park Geun-hye will get a warm welcome during a four-day state visit that begins on Thursday.
"I am sure this summit will be an unprecedented honeymoon for China and South Korea," said Woo Su-keun, a South Korean professor at Donghua University in Shanghai.
The contrast between China's relationship with South Korea and its testy ties with the erratic North could not be starker.
Beijing, the closest thing North Korea has to a major ally, has grown frustrated with Pyongyang and was heavily involved in U.N. sanctions imposed for the North's third nuclear test in February. Its annual trade with North Korea is a puny $6 billion, versus $215 billion with the South.
On top of that, ordinary Chinese love South Korean fashion, pop stars and soap operas. North Korea, by contrast, is seen as a dangerous liability, and Chinese refer to leader Kim Jong-un derisively on social media as "Fatty Kim".
Helping the mood music for Park, a slightly built and elegant 61-year-old, China's relations with Japan are also in the deep freeze due to a row over disputed islands in the East China Sea.
Park's trip follows two visits by North Korean envoys to Beijing in the past month. While North Korea offered talks on its nuclear programme during those visits, experts are sceptical Pyongyang is ready to make any concessions.
North Korea will be high on the agenda when she meets Chinese President Xi Jinping, who in a telephone call in March after both leaders took office called Park "an old friend of the Chinese people and of myself", according to South Korean officials.
Both are expected to agree Pyongyang must give up its nuclear weapons. Park might also be able to use her personal chemistry with Xi - who she first met over lunch at a Chinese restaurant in Seoul in 2005 - to get China to put more pressure on Pyongyang, experts said.
"Out of frustration and scepticism over a decade of North Korea's nuclear weapons development, China is now stepping up its push for denuclearisation," said Lee Soo-hyuck, a former South Korean deputy foreign minister and its chief envoy to disarmament talks between 2003 and 2005.
However, China is highly unlikely to do anything that would cause the collapse of North Korea, which it sees as a strategic land buffer against American influence in the region.
Park and Xi will also focus on forging a stronger economic partnership.
The South Korean leader will take a big business delegation to China, including executives from Samsung Electronics Co Ltd and Hyundai Motor although it was unclear if any deals will be signed. Park's office expects a bilateral free trade pact under negotiation to be discussed.
China is South Korea's biggest trading partner. South Korea is also one of the few developed countries that runs a surplus with China - to the tune of $53 billion in 2012 according to Seoul - thanks to exports of cars, smartphones, flat screen TVs, semiconductors and petrochemicals.
South Korean imports to China overtook Japan last September, Singapore's DBS Bank said in a recent research note.
Hyundai and its Kia Motors affiliate are now the third biggest seller of cars in China, ahead of their Japanese rivals. Volkswagen AG and General Motors are the top two.
South Korean investment has also poured into China, exceeding $40 billion since 1988.
After meetings in Beijing, Park will visit Xi'an, an industrial city in northwestern China where Samsung, the world's top technology firm by revenue, is building a $7 billion chip complex. Hyundai has just completed its third plant in Beijing.
TIES THAT BIND
When China and North Korea sealed their relationship in blood fighting side by side in the Korean War, both were poor and isolated against the West. North Korea remains poor to this day while China is the world's second largest economy and South Korea is an industrial powerhouse.
Beijing only established diplomatic relations with South Korea in 1992, but ties have flourished since.
In 2005, when Xi was Communist Party boss of the wealthy eastern coastal province of Zhejiang, he met Park for lunch.
Xi was keen to learn about the economic New Village Movement, a rural development program in the 1970s undertaken by Park's father, military ruler Park Chung-hee who is credited with building modern South Korea.
Park, according to South Korean media reports, later gave Xi two boxes of materials that included her father's speeches on the movement and a book about South Korean economic development.
She is an admirer of Chinese culture and her favourite book is a "History of Chinese Philosophy" by philosopher Feng Youlan. She has spoken fondly of her earlier trips to China.
"President Park has a soft spot for China," the official China News Service said. "This kind of friendly public diplomacy gives a good impression to Chinese people and is extremely important."