• In COVID-19 total lockdown in Spain, the well-being of children was disrupted. • Physical, creative and leisure activities reported the lowets levels of well-being. • Girls show more positive emotional expression, adapting better to locdown. • Youngest children indicated greater well-being and less academic preasure. • Children with outdoor space in their homes showed higher levels of general well-being. The Covid-19 pandemic is having an unprecedented impact on societies. In the interest of maintaining social distancing, schools in many countries have closed their doors and children have been confined to their homes. Thus, the objective of the present study was to holistically analyze the well-being of children during a period of full lockdown in Spain, by considering physical, emotional, social, and academic indicators. The scale "Well-being of Children in Lockdown" (WCL) was used to measure the well-being of 1225 children from 2 to 12 years old from Northern Spain. The survey was completed by the parents and was designed to analyze children's well-being in terms of physical, emotional, social and academic aspects. The results suggest that the general well-being of children during lockdown was at an intermediate level. Analysis of the various measures of well-being revealed that the lowest levels were obtained for physical activity, along with creative and playful activities. Girls, younger children, and those who have access to an outdoor space showed the greatest levels of well-being. Finally, we discuss the implications of these findings for the well-being of children and, in particular, how this can be improved amid the current Covid-19 crisis. [ABSTRACT FROM AUTHOR]