Objectives. We sought to determine whether the exclusion of adults without mobile telephone access may bias estimates derived from political behaviour -related telephone surveys.

Methods. We took data from the European Social Survey (ESS) 2006/07 and used logistic regression to compare the odds of political related behaviour for adults with xed phone access to those for adults with mobile telephone access and those without telephone access.

Results. When interviewed, adults in households did not have telephones it varied from 0 in Sweden to 23,1% in Russian Federation and the rate of all households have only mobile telephone access varied from 1% in Switzerland to 50 % Finland. Relative to all adults, adults with mobile telephone access had lower odds of vote in the last national election and had lower odds of political interest, watching news and politics in TV and lower odds in reading newspaper about politics or current aairs on average weekday Conclusion. As people substitute mobile telephones for xed telephones (the percentage is currently for eight countries under 12 % low) which minimizes the bias resulting from their exclusion from telephone surveys. In twelve countries the percentage is currently more than 20 % high. Their exclusion from telephone surveys could increase the bias. Bias between ten through twenty percentage point is expected for estimates of voting last national election, for about 20 countries.