Carbazole-based oligomeric and polymeric materials have been studied for almost 25 years for their unique electrical electrochemical and optical properties. Interestingly, carbazole units can be linked in two different ways leading to either poly(3,6 carbazole) or poly(2,7 carbazole) derivatives. While the former class seems to be very interesting for electrochemical and phosphorescence applications, the latter shows very promising optical properties in the visible range for light emitting diodes (LED). the major intrinsic difference between these two classes is the effective conjugation length: poly(2,7-carbazole) materials having the longer one, due to their poly(p-phenylene)-like structure. Using different synthetic strategies and substitution patterns, the physico-chemical properties of both classes can be fine-tuned, leading to high performance materials for a large number electronic applications.