Background Population-based cervical cancer screening (CCS) are deemed to be more cost-effective than opportunistic screening and to reduce inequalities. Implementation in Portugal has been heterogeneous, at the regional level. In Amadora healthcare cluster (Lisbon area), implementation started in April 2018 in a pilot unit and was scaled-up. We aimed to assess population-based CCS implementation in Amadora. Methods Population-based CCS targets women aged 30-65, and utilises liquid-based cytology with partial HPV genotyping (HPV16/18 and other high-risk HPV - hrHPV). Samples positive for other hrHPV undergo a cytology. HPV16/18+ and other hrHPV+ with ≥ASCUS (atypical squamous cells of undetermined significance) are referred to colposcopy. We assessed implementation according to key indicators extracted from our information system: geographic coverage, number of tests, positive results, positive predictive value of referral (number of cervical intraepithelial neoplasia-CIN/number colposcopies). Results As of 30 August 2019, CCS were in place in 4 of the 9 units, potentially covering 20904 women (48.4% of the target population). 1797 womem performed screening within the programme. Invitation for screening is currently implemented in 1 of the 4 units. Screening results were available for 1702 women, 11,1% were HPV+. From these, 26,5% were HPV 16/18+ and 86.2% positive for other hrHPV. Among the latter, 63.2% were negative for intraepithelial lesion and 36.8% were ≥ASCUS. Overall, of these 189 women, 51.3% (n = 97) were referred for colposcopy. Colposcopy results were available for 37 women, of which 13 had a CIN. PPV of referral was 35.1% (95%confidence interval: 20.7;52.6). Conclusions Despite being a population-based screening most tests are still opportunistic. There is still a limited number of colposcopies results but the current PPV of referral is low and requires further investigation. Implementation towards a full population-based screening in Amadora should continue. Key messages Implementation of a population-based cervical cancer screening in Amadora, Portugal is underway but most screening tests are still applied in an opportunistic manner. A limited number of results is avaliable to estimate positive predictive value of referral to colposcopy. Results available indicate a value of 35.1%, which requires further investigation.