Immediately after the ruling, Ethiopia declared it had won the land it claimed and Eritrea had lost the case, just as it had lost the war.
Eritrean state television denounced the Ethiopian comments as a lie.
A number of key towns and villages have been awarded to Ethiopia.
Click here to see a map of the region
Zalembessa - the scene of heavy fighting - has gone to Ethiopia, as have the towns of Alitena - in the central sector of the border - and Bada in the east.
Eritrea appears to have made some gains in the west.
But the BBC's Martin Plaut says the details of the complex award are hard to decipher, and it will be some time before it is clear who the winners and losers in the judgement have been.
Diplomats say both governments are putting forward their diametrically opposed views of the ruling to convince their citizens that the sacrifices and loss of life have not been in vain.
On Sunday, Ethiopian state radio interrupted regular programmes to broadcast patriotic music and victory songs, and several thousand people demonstrated in Addis Ababa.
In Eritrea, some residents expressed relief at the ruling which they hope will allow them to get on with their lives.
Peace deal
Fighting broke out in May 1998 when Eritrea - which had won independence from Ethiopia in 1993 - invaded territory Ethiopia considered to be within its national borders.
After months of heavy fighting, Ethiopian troops captured much of the smaller country's prime agricultural land.
Eritrea, which has a population of 3.5 million compared to Ethiopia's 65 million, agreed to end hostilities in June 2000.
A peace deal was signed six months later and set the terms for the border commission.
But relations have remained strained and the United Nations has 4,200 peacekeepers patrolling a buffer zone around the disputed areas.