Sedentary behaviours (SB) in children, independent of moderate-to-vigorous physical activity, have being associated with an increased obesity risk [1, 2]. During week-days, children spend almost half of their waking hours at school, of which 50 – 70% is spent sitting [3, 4]. Introducing desks that allow children to stand during lessons has the potential to reduce children’s overall sitting and prevent unhealthy increases in adiposity and cardiometabolic risk factors [5, 6]. The aim of this study was to determine the impact of sit-stand workstations use over 8-months on waist circumference (WC), body mass index (BMI), blood pressure (BP) and school sitting time (SST) on 11-year old children. In this single-school study, one year-6 class (24 students) was randomly assigned as an intervention classroom (IC) and another year-6 class (24 students) as a control classroom (CC). The IC was equipped with sit-stand workstations and the teacher was instructed in the delivery of pedagogical classroom sitting-reduction strategies, whereas the CC followed standard pedagogical practice and retained traditional classroom furniture. Linear-mixed models were utilized to estimate the effects of the intervention on SST, WC, BMI and BP. There were no significant between-group differences at baseline and no significant intervention effect after 8-months for all the variables. However, both groups decreased their overall SST by 13.66 and 20.83 minutes per day. The average diastolic BP was reduced in 2.01 and 2.44 mmHg for CC and IC respectively, whereas the IC slightly decreased BMI on 0.41 kg/m2. WC and systolic BP similarly increased in both groups. In conclusion, despite the absence of significant differences, there was a trend to observe greater positive effects in the IC, indicating that, to better establish significant effects of height-adjustable desks on adiposity and cardiometabolic risk factors, larger, longer-term trials with multiple schools and bias (contamination) control are required.