BACKGROUND: Sickle cell disease (SCD) patients have impaired domains of health-related quality of life (HRQOL). Hydroxyurea is safe and efficacious in SCD; however, adherence is suboptimal, and patients' perceptions are poorly understood amongst adolescents and young adults (AYA). Study objectives were to: (1) examine patients' perceptions of SCD and hydroxyurea; and (2) explore the relationship of their perceptions to clinical characteristics, HRQOL domains and hydroxyurea adherence. METHODS: Thirty-four SCD patients on hydroxyurea (>/=6 months) participated in a single-institution study. Study measures included Brief-Illness Perceptions Questionnaire, (c)Modified Morisky Adherence Scale 8-items, and Patient Reported Outcomes Measurement Information System (PROMIS(R)). We assessed the relationship of patients' perceptions to hydroxyurea adherence using Wilcoxon rank-sum test, the number of hospitalizations using Kruskal-Wallis test, and the number of ED visits, adherence level, HRQOL domain scores using Spearman's rho correlations. We conducted a sub-analysis in HbSS patients to evaluate the relationship of patients' perceptions to laboratory markers of hydroxyurea adherence. RESULTS: Participants were 59% male and 91% Black, and had a median age of 13.5 (range 12-18) years. Participants with >/=4 hospitalizations over 1-year prior (using electronic medical chart review) reported more negative perceptions of SCD-related symptoms and emotional response, and perceived hydroxyurea as less beneficial; all p-values =0.01. Most participants (74%) reported low hydroxyurea adherence. Participants with higher hydroxyurea adherence perceived more hydroxyurea benefits (r s = 0.44, p < 0.01) and had better emotional response to SCD (r s = -0.44, p = 0.01). In a sub-analysis of HbSS patients, perceived benefits of hydroxyurea positively correlated with HbF (r s = 0.37, p = 0.05) and MCV values (r s = 0.35, p = 0.05). Participants with more negative perceptions of SCD-related consequences, concerns, and emotional response, and fewer perceived hydroxyurea benefits reported worse fatigue (r s = 0.68; r s = 0.44; r s = 0.74; r s = -0.60), pain (r s = 0.56; r s = 0.54; r s = 0.63; r s = -0.39), anxiety (r s = 0.55; r s = 0.58; r s = 0.56; r s = -0.47), and depression (r s = 0.64; r s = 0.49; r s = 0.70; r s = -0.62), respectively, all p-values <0.05. CONCLUSIONS: Dynamics influencing hydroxyurea adherence are multifactorial, and understanding patients' perceptions is critical to overcoming adherence barriers. Patients' favorable perceptions correlated with greater adherence and better HRQOL domain scores. Prospective evaluation of patients' perceptions of SCD and hydroxyurea in relation adherence, HRQOL domains and clinical outcomes is warranted.