Republic of Ireland 0-2 Serbia
Tom Mohan's side failed to hit top gear in a scrappy game on a bumpy pitch and the Irish head coach was disappointed with the concession of two soft goals in either half.
Stefan Ilić put the Serbs ahead in the 24th minute when he turned the ball home after Ireland were caught on the break following a free-kick that was cleared by the Serbian side and the Irish failed to see out the danger.
Serbia added their second goal through Dejan Joveljić in the 61st minute after the Irish failed to clear a dangerous cross.
"It was a disappointing result and it was a poor game on a bad pitch. Serbia were a big side who took no chances on a very hard pitch and played the conditions better than we did," said Mohan.
"The two goals were poorly defended and it was frustrating. Our mistakes were punished while there's weren't. We had three reasonable chances late on but overall it was a stop start game that suited them better than us.
"We'll just have to get ourselves back into the right frame of mind for our next game against Macedona on Wednesday."
REPUBLIC OF IRELAND: Travers, Carroll, Wilson, O'Shea, Browning (McKenna 51), L. O'Connor, Molumby, Byrne, Scully (McAuley 68), Mallon (O'Sullivan 51), O'Driscoll.
SERBIA: A. Popović, J. Popović, Devetak (Terzić 59), M. Ilić, Bosnjak, Jovanović, Maksimović (L. Ilić 73), Joveljić, N. Petrović, Đerlek (Mišković 66), S. Ilić.
FIXTURES
Monday, March 28
UEFA U17 Championships Elite round Group 7
Republic of Ireland 0-2 Serbia, MZOS Znicz, Pruszkow (POL)
Wednesday, March 30
UEFA U17 Championships Elite round Group 7
Republic of Ireland v Montenegro, Stadion ROSRRiT Siedlce, Siedlce (POL) (1.00pm)
Saturday, April 2
UEFA U17 Championships Elite round Group 7
Poland v Republic of Ireland, MZOS Znicz, Pruszkow (POL) (5.00pm)