Resumen: Aims: We aim to study the the reliability and factorial structure of the Postpartum Bonding Questionnaire (PBQ)administered through two different formats, offline (paper-and-pencil) and online. We also compared clinical, obstetrical, reproductive, and psychopathological variables related to poor mother infant bonding (MIB). Methods: A cross-sectional study was conducted on 1, 269 mothers. The offline group included 812 women who attended a 40-day postpartum clinical appointment. The online group consisted of 457 women recruited during admission for delivery who volunteered to carry out the online protocol 40 days postpartum. All the participants individually completed the PBQ, the Edinburg Postnatal Depression Scale (EPDS) and other clinical and sociodemographic variables. Results: The 4-factor solution proposed in the PBQ and its Spanish validation showed good model fit for both samples. Online participants reported higher levels of stress, depressive symptoms, and poor bonding, specifically on PBQ scores and the Rejection and Anger subscales. No differences were found in both samples regarding the type of statistical associations between PBQ and sociodemographic, reproductive, obstetric and psychological outcomes. Conclusion: Online assessment may be an appropriate option for detecting possible alterations in MIB due to the reduction of desirability bias, the increased perception of anonymity, and being a more cost-effective method. Idioma: Inglés DOI: 10.1080/02646838.2021.1921716 Año: 2022 Publicado en: JOURNAL OF REPRODUCTIVE AND INFANT PSYCHOLOGY 40, 5 (2022), 500-515 ISSN: 0264-6838 Factor impacto JCR: 2.5 (2022) Categ. JCR: PSYCHOLOGY, MULTIDISCIPLINARY rank: 67 / 147 = 0.456 (2022) - Q2 - T2 Factor impacto CITESCORE: 5.5 - Medicine (Q2) - Psychology (Q1)