With an investment in bonds or with granting loans the risk of issuers not being able to repay bonds or not being granted loans anymore arises. The credit default swap (CDS) is a financial contract to hedge a default of a bond or a loan. With the occurrence of the financial crisis 2007/2008 this kind of credit derivative has been publicly spotlighted, especially concerning their speculation possibilities. In this master thesis the emphasis is on the valuation of CDSs. At first basic information regarding definitions for a better understanding, the historical development of credit derivatives as well as elements, modes and possible applications of credit derivatives, such as CDSs, is explained. At the beginning of the main part the description and the comparison of the valuation models, single as well as portfolio, is presented, but only the single models are simulated and analysed concerning their sensitivity. A segmentation of single models in structural, reduced-form and rating based models plus a classification of portfolio models is conducted. After a characterisation of general influences on the models, the simulation based on self-constructed examples and on literature examples follows. The sensitivity is analysed with the rearrangement of parameters used in the models. In the last part of this thesis single models are compared with each other, based on the simulation results as well as on the sensitivity analysis, so short descriptions regarding the data bases, the necessary processes and the complexity can be generated.