Background. Attitudes towards bullying at school are influential in understanding and preventing bullying behaviour but they should be measured with reference to the particular conditions under which bullying takes place. Aims. To establish how far positive and negative judgments of bullying and victims and blaming of the victim vary according to the gender of observers, gender of bullies and of victims and whether the bullying took place alone or in group. Sample. Participants were 117 students (49 boys and 68 girls), aged 11-12, recruited from a middle school in Italy randomly allocated to one of four independent groups according to experimental condition: bullying alone among girls, bullying alone among boys, bullying in groups among girls, bullying in groups among boys. Method. Participants watched one of four versions of a video according to experimental condition showing a brief standardized bullying episode taking place at a school; they then had to fill in a self-report questionnaire measuring the dependent variables: respondents' positive or negative judgments towards the bully and the victim shown in the video and how far the victim was blamed for what had happened. Results. Overall, results indicate students have positive attitudes towards the victims of bullying and tend not to blame them for what has happened. However, same gender identification lead girls to blame male victims more than female victims and the reverse applies in case of boys providing their judgments. A bully acting alone is considered stronger and braver than when acting in a group. Conclusions. The limits and potential of the study are presented with special attention to implications for intervention strategies in school by focusing on the role observers could play in supporting the victims and discouraging the bullies.