It was Darlington's experienced campaigners who proved decisive as Craig Hignett, Clyde Wijnhard and Alun Armstrong were all involved in the three goals as Darlington proved that they are a force to be reckoned with.
There was an element of luck about the first goal as Orient captain Alan White turned a low cross from Hignett past his own keeper Glen Morris after only four minutes.
Hignett was a menace throughout in midfield and he could yet prove to be the lucky charm that will take David Hodgson's side onwards and upwards.
The first half was highly entertaining and the visitors could count themselves unlucky not to be at least on level terms at the break. Indeed soon after Darlington's opener, Wayne Carlisle went close to levelling the scores from a 25-yard free-kick in the seventh minute.
But upfront, former Leeds United striker Clyde Wijnhard proved to be a handful for the visitors defence and the big Dutchman went close to increasing his side's tally in the 23rd minute, but he headed Neil Wainwright's cross onto the top of the net.
The visitors responded and it was Carlisle again who went close with a shot that flew over the crossbar in the 26th minute.
Captain Alan White almost grabbed an equaliser but again his header was off target and he was involved again soon afterwards when denying Clyde Wijnhard at the other end with a last-ditch tackle.
In the second half, Darlington increased their lead in the 58th minute when Wijnhard stooped to head a Neil Wainwright cross high into the net giving Glen Morris no chance.
The goal seemed to deflate the visitors and it was no surprise when the home side increased their lead in the 74th minute. Armstrong notched his eighth goal for Darlington when he chipped the ball over the advancing Morris and into the unguarded net.
In the dying seconds, Armstrong had another opportunity. Wijnhard picked him out inside the area and the former Middlesborough striker curled a shot that was plucked out of the air by Morris.