Recombinant antibodies are the most important class of biopharmaceuticals. They are commonly produced in recombinant Chinese Hamster Ovary (CHO) cells. Traditional concepts for the creation of such cell lines rely on the random integration of the plasmid, containing the gene of interest, in the genome. To preselect a transcriptionally active genomic locus prior to transfection the recombinase mediated cassette exchange (RMCE) was developed. The recombinase Flipase recognises distinct DNA sequences and by the use of heterospecific recognition sites a cassette exchange is possible. Within this study, the two anti HIV-1 antibodies 2F5 and 3D6, both designed as single chain Fv-Fc (scFc) variant, were produced and compared by this technique. Therefore a RMCE competent CHO host cell line was cotransfected with either 2F5scFc or 3D6scFc and the enzyme Flipase. The twelve best producing clones of each scFc producing cell line were grown in T25 flask and the two best producers of each were selected for cultivation in spinner flasks. Those four cell lines were intensively characterised and special emphasis was laid on the detailed investigation of the RMCE. This characterisation was done by FISH and quantitative real time PCR. It turned out, that one cell line harboured an additional transgene copy, although the three other cell lines had the same gene copy number as the cell line prior to cassette exchange. Another difference was the higher specific productivity of the 3D6scFc producing cell lines, although the transcript level, specific growth rate and the metabolism remained almost the same in all scFc producing cell lines. Only the intercellular product formation was slightly higher for 3D6scFc producing cell lines than for 2F5scFc producing cell lines, but not in the dimension of the specific productivity. This study demonstrated the ability of RMCE for recombinant protein production and also the influence of the product itself on the specific productivity.