The bog of Robenhausen near Seegräben-Wetzikon (Zurich Oberland) belongs to a peatland complex in the nature conservation area of the Lake of Pfäffikon which is surrounded by glacial deposits such as moraines and drumlins. For more than 200 years peat has been used as source of fuel. Since 1996 the bog has become an important nature-conservation and regional recreation area. Primary and secondary peat build-up processes have been studied at 12 core drilling sites within this peat bog. Different kinds of peat have been analysed for plant macro- and microfossils, the degree of peat decomposition and the ratio of organic and inorganic material. In most cases, core samples provided only small amounts (or none) of primary peat, i.e. most peat was secondary and originated mainly from transition moors and raised bogs containing the Spagnum species. Once peat cutting had stopped, peat bog growth at most sites started with an eutrophic fen-peat and built up 5–70 cm of secondary peat. Typical plants are from the Carex species, Phragmites communis, Cladium mariscus, Molinia caerulea, Calluna vulgaris, Frangula alnus, Drosera spec. and the Sphagnum species. Other mosses found locally are Betula pubescens and Pinus sylvestris. Profiles taken in the peat bog show that the degree of organic decomposition increases from top to bottom. Some profiles from sites close to the lake shore show an undisturbed build-up of primary peat. This has been caused through a lowering of the sea level during the 1860’s. Small secondary stands of hairy birch and Scots Pine are approx. 50 years old (peat cutting stopped ca. 1950). This study provides detailed information to peat bog regeneration dynamics after a long period of peat cutting. Furthermore, these results can be used to help maintain this important peatland complex.