Web surveys are promising another break-throu improvement to the survey industry. However, as usual, initial suspicions towards new methods are generally very strong, which could also be observed previously for other modes of computer assisted interviewing. During the few years of their existence Web surveys provided us with a wide range of empirical evidence. Many advantages of this survey mode are reported (Balden 1999; Batagelj and Vehovar 1998a; Bates and Nichols 1998; Black 1998; Chisholm 1998; Clayton and Werking 1998; Comley 1997, 1998; Coomber 1997; Davis 1998; Dillman and Tortora 1998; Eaton 1997; Farmer 1998; Gonier 1999; Hollis 1999; Iyer 1996; Kehoe and Pitkow 1996; Kottler 1997a; Lanier et al. 1998; McCullough, 1998a; Nichols and Sedivi, 1998a; Onyshkevych and McIndoe 1999; Parackal and Brennan, 1998; Pitkow and Kehoe, 1995; Pitkow and Recker 1995; Schillewaert et al. 1998; Smith 1997; Spaeth 1999; Stanton 1998; Watt 1997; Weissbach 1997; Wydra 1999), however, certain obstacles do exist, particularly when the general population is targeted. Leaving some (temporary) technical problems aside, the key problems remain the Intemet penetration within the general population and, even more seriously, the participation m these surveys. In this paper we concentrate on the specific aspect of Web surveys, ie using the post-survey weighting corrections as a remedy for these problems. These post-survey adjustments are not specific only to the Web surveys but are frequently discussed also in the context of the general non-response problem in other survey modes. Here, we discuss the problem within a framework of an empirical project based on comparisons of the results from a Web and a telephone survey.