ABSTRACT Objective: to investigate factors associated with the use and quality of Primary Health Care, as well as the occurrence of pneumonia and diarrhea in children under one year. Method: cross-sectional study conducted with 317 caregivers of 56 Family Health teams from Juazeiro do Norte, Ceará, from August 2014 to October 2015, using the child version of the Primary Care Assessment Tool, child version. Results: in the logistic adjustment, children received assistance (OR: 0.54; 0.32-0.91) and accessibility to the Primary Health Care Unit (OR: 0.49; 0.31-0.76). identified as possible protective factors for episodes of diarrhea. The variables associated with pneumonia were unsatisfactory access (ORaj: 2.13; 95% CI 1.18-3.82), a likely risk factor, and coordination (ORaj: 0.33, 95% CI 0.12-0,94), as a probable protection factor. Conclusion: primary care attendance resulted in a higher chance of avoiding hospitalization for pneumonia, a condition considered sensitive to care in this care model. Complementing family income and children's accessibility to the health unit were protective factors for episodes of diarrhea. The search to ensure the presence and extension of the Primary Health Care attributes has the potential to positively modify the child's health and, therefore, both should be ensured as rights of this population.