We will present new results of our ongoing multiplicity study of exoplanet host stars 
carried out in the infrared, using several telescopes and detectors on the northern and 
southern hemisphere, among those SofI at ESO-NTT and SDI/NACO at ESO-VLT. We will report on 
our observations of newly found planet hosting stellar systems; e.g. some new binary systems 
composed of an exoplanet host star and a low-mass stellar companion, as well as one new 
planet hosting triple star system. Furthermore, we show the spectroscopic confirmation of a 
new white dwarf companion of an exoplanet host star and our infrared imaging data of the 
first directly detected brown dwarf companion of an exoplanet host star, observed with SofI. 
Finally, we will discuss the properties of exoplanets in stellar systems and compare their 
properties (orbital elements, minimum-masses, angular momenta) with the Properties of 
planets orbiting around single stars. Differences between the properties of planets 
revolving around a component of a stellar system and those of planets which are in orbit 
around an isolated single star might probably point out that the stellar multiplicity alters 
either the formation or the evolution process of planets.