Carbon nanofiber (CNF) has been extensively produced as it shows outstanding physical properties which can be exploited in many applications. In addition to a long and straight nanofiber, several irregular configurations of CNF could be observed in a certain particle catalyst, reaction conditions and experimental techniques. One of the ways is by synthesizing carbon nanofiber using catalytic chemical vapor decomposition (C-CVD) method. This can be achieved by using Fe2O3 and NiO as the catalysts with ethylene and hydrogen as the carbon feedstock and carrier gas, respectively. The results from TEM analysis show that irregular CNF configurations are formed such as coiled, regular helical and twisted coil as well as corrugated CNF. © Springer-Verlag Berlin Heidelberg 2010.