Warm absorbers are an important new tool for investigating the conditions within the central regions of active galaxies .
They have been observed in \sim 50 % of the well-studied Seyfert galaxies and have also been detected in quite a number of Narrow-line Seyfert 1 galaxies ( NLSy1 ) .
Here , we present a study of the X-ray properties of several NLSy1s with focus on their warm absorbers : ( a ) An analysis of all ROSAT PSPC observations of NGC 4051 including new ones is performed , which reveals variability by a factor \sim 30 in count rate and much less variability in the warm absorber parameters .
( b ) The possibility of a dusty warm absorber in IRAS 13349+2438 is explored on the basis of photoionization models for dusty warm gas and explicit ROSAT spectral fits .
( c ) The X-ray spectrum of the NLSy1 1E 0117.2-2837 is analyzed .
It can be successfully described by a very steep powerlaw of photon index \Gamma _ { x } \simeq - 4 , or alternatively by a warm-absorbed flat powerlaw .
UV-EUV emission lines expected to arise from the warm material are predicted .
( d ) The strong spectral variability of RX J0134.3-4258 ( from \Gamma _ { x } \simeq - 4.4 in the ROSAT survey observation , to \simeq - 2.2 in our subsequent pointing ) is examined in terms of warm absorption .