A series of poly(norbornenes) with pendant triarylamine (TPA) groups has been synthesized by ring-opening metathesis polymerization and investigated as hole transport materials in organic two-layer light-emitting diodes (LEDs). Efficient device fabrication through spin casting of the hole transport layer (HTL) was possible, since the polymers exhibited excellent film formation properties. LEDs of the form ITO/poly(norbornene)-TPA/Alq3/Mg (ITO = indium tin oxide, Alq3 = tris(8-quinolinato)aluminum) showed bright green emission with external quantum efficiencies of up to 0.77% (1.30 lm/W) for 20 nm thick HTL films. The length and polarity of the linker between the triarylamine functionality and the polymer backbone were varied systematically. The device performance was found to depend strongly on these structural differences. Substitution of ester groups by less polar ether functionalities greatly enhances external quantum efficiencies, lowers the operating voltage, and improves the stability of the device....