Lunin and Maldacena recently found a simple method to generate AdS_5 supergravity backgrounds dual to exactly marginal deformations of SCFTs. In the first part of the talk, we will consider extensions to AdS_4 backgrounds, concentrating on those for which dual IR 3d field theories have been proposed. In the second part, we will concentrate on the deformation of N=4 SYM in 4d and analyze a certain Penrose limit. We will be led to consider a 'modified Landau problem' and relate it to the different set of chiral operators of the deformed N=4.